staging: exfat: stopusing CONFIG_FAT_DEFAULT_IOCHARSET

When CONFIG_VFAT_FS is disabled, the reference to CONFIG_FAT_DEFAULT_IOCHARSET
causes a link failure:

drivers/staging/exfat/exfat_super.c:46:41: error: use of undeclared identifier 'CONFIG_FAT_DEFAULT_IOCHARSET'
static char exfat_default_iocharset[] = CONFIG_FAT_DEFAULT_IOCHARSET;

I could not figure out why the correct code is commented
out, but using that fixes the problem.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20190906150917.1025250-1-arnd@arndb.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/exfat_super.c

@@ -37,11 +37,8 @@
 
 static struct kmem_cache *exfat_inode_cachep;
 
-// FIXME use commented lines
-// static int exfat_default_codepage = CONFIG_EXFAT_DEFAULT_CODEPAGE;
-// static char exfat_default_iocharset[] = CONFIG_EXFAT_DEFAULT_IOCHARSET;
-static int exfat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
-static char exfat_default_iocharset[] = CONFIG_FAT_DEFAULT_IOCHARSET;
+static int exfat_default_codepage = CONFIG_EXFAT_DEFAULT_CODEPAGE;
+static char exfat_default_iocharset[] = CONFIG_EXFAT_DEFAULT_IOCHARSET;
 
 #define INC_IVERSION(x) (inode_inc_iversion(x))
 #define GET_IVERSION(x) (inode_peek_iversion_raw(x))