Fix a debug-only build error in ext2/xattr.c:

When building without extra debugging, (and with another patch that uses
no_printk() instead of <empty> for the ext2-xattr debug-print macros,
this build error happens:

../fs/ext2/xattr.c: In function ‘ext2_xattr_cache_insert’:
../fs/ext2/xattr.c:869:18: error: ‘ext2_xattr_cache’ undeclared (first use in
this function); did you mean ‘ext2_xattr_list’?
     atomic_read(&ext2_xattr_cache->c_entry_count));

Fix the problem by removing cached entry count from the debug message
since otherwise we'd have to export the mbcache structure just for that.

Fixes: be0726d3 ("ext2: convert to mbcache2")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jan Kara <jack@suse.cz>