staging: erofs: disable compiling temporarile

As Stephen Rothwell reported:

"After merging the staging tree, today's linux-next build (x86_64
allmodconfig) failed like this:

drivers/staging/erofs/super.c: In function 'erofs_read_super':
drivers/staging/erofs/super.c:343:17: error: 'MS_RDONLY' undeclared (first use in this function); did you mean 'IS_RDONLY'?
  sb->s_flags |= MS_RDONLY | MS_NOATIME;
                 ^~~~~~~~~
                 IS_RDONLY
drivers/staging/erofs/super.c:343:17: note: each undeclared identifier is reported only once for each function it appears in
drivers/staging/erofs/super.c:343:29: error: 'MS_NOATIME' undeclared (first use in this function); did you mean 'S_NOATIME'?
  sb->s_flags |= MS_RDONLY | MS_NOATIME;
                             ^~~~~~~~~~
                             S_NOATIME
drivers/staging/erofs/super.c: In function 'erofs_mount':
drivers/staging/erofs/super.c:501:10: warning: passing argument 5 of 'mount_bdev' makes integer from pointer without a cast [-Wint-conversion]
   &priv, erofs_fill_super);
          ^~~~~~~~~~~~~~~~
In file included from include/linux/buffer_head.h:12:0,
                 from drivers/staging/erofs/super.c:14:
include/linux/fs.h:2151:23: note: expected 'size_t {aka long unsigned int}' but argument is of type 'int (*)(struct super_block *, void *, int)'
 extern struct dentry *mount_bdev(struct file_system_type *fs_type,
                       ^~~~~~~~~~
drivers/staging/erofs/super.c:500:9: error: too few arguments to function 'mount_bdev'
  return mount_bdev(fs_type, flags, dev_name,
         ^~~~~~~~~~
In file included from include/linux/buffer_head.h:12:0,
                 from drivers/staging/erofs/super.c:14:
include/linux/fs.h:2151:23: note: declared here
 extern struct dentry *mount_bdev(struct file_system_type *fs_type,
                       ^~~~~~~~~~
drivers/staging/erofs/super.c: At top level:
drivers/staging/erofs/super.c:518:20: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .mount          = erofs_mount,
                    ^~~~~~~~~~~
drivers/staging/erofs/super.c:518:20: note: (near initialization for 'erofs_fs_type.mount')
drivers/staging/erofs/super.c: In function 'erofs_remount':
drivers/staging/erofs/super.c:630:12: error: 'MS_RDONLY' undeclared (first use in this function); did you mean 'IS_RDONLY'?
  *flags |= MS_RDONLY;
            ^~~~~~~~~
            IS_RDONLY
drivers/staging/erofs/super.c: At top level:
drivers/staging/erofs/super.c:640:16: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .remount_fs = erofs_remount,
                ^~~~~~~~~~~~~

Caused by various commits creating erofs in the staging tree interacting
with various commits redoing the mount infrastructure in the vfs tree.

I have disabed CONFIG_EROFS_FS for now:"

The reason of compiling error is:

Since -next collects and merges developing patches including common vfs
stuff from multi-trees, but those patches didn't cover erofs, such as:

('vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled")
https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/commit/?h=for-next&id=109b45090d7d3ce2797bb1ef7f70eead5bfe0ff3

("vfs: Require specification of size of mount data for internal mounts")
https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/commit/?h=for-next&id=0a191e4505a4f255e6513b49426213da69bf0e80

Above vfs related patches has not been merged in staging tree, if we
submit those erofs patches to staging mailing list and after including
them in staging-{test,nexts} tree, it can easily cause compiling error.

We worked out some patches to adjust those vfs change, but now we just
submit them to -next tree temporarily to avoid compiling error.

For potentail conflict in between erofs and vfs changes in incoming
merge window, Stephen suggested that we can disable CONFIG_EROFS_FS
temporarily to pass merge window, and after that we can do restore by
reenabling CONFIG_EROFS_FS and applying those fixing patches. Also
Greg confirmed this solution.

So, let's disable compiling erofs for a while.
Suggested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/Kconfig

@@ -2,7 +2,7 @@
 
 config EROFS_FS
 	tristate "EROFS filesystem support"
-	depends on BLOCK
+	depends on BROKEN
 	help
 	  EROFS(Enhanced Read-Only File System) is a lightweight
 	  read-only file system with modern designs (eg. page-sized