common/casefold: support f2fs

Now, f2fs has ported casefold feature from ext4, let's enable the
testcase.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/casefold

@@ -9,6 +9,9 @@ _has_casefold_kernel_support()
 	ext4)
 		test -f '/sys/fs/ext4/features/casefold'
 		;;
+	f2fs)
+		test -f '/sys/fs/f2fs/features/casefold'
+		;;
 	*)
 		# defaults to unsupported
 		false
@@ -46,6 +49,9 @@ _scratch_mkfs_casefold()
 	ext4)
 		_scratch_mkfs -O casefold $*
 		;;
+	f2fs)
+		_scratch_mkfs -C utf8 $*
+		;;
 	*)
 		_notrun "Don't know how to mkfs with casefold support on $FSTYP"
 		;;
@@ -58,6 +64,9 @@ _scratch_mkfs_casefold_strict()
 	ext4)
 		_scratch_mkfs -O casefold -E encoding_flags=strict
 		;;
+	f2fs)
+		_scratch_mkfs -C utf8:strict
+		;;
 	*)
 		_notrun "Don't know how to mkfs with casefold-strict support on $FSTYP"
 		;;