Btrfs: make set/get functions for the super compat_ro flags use compat_ro

Our set/get functions for compat_ro_flags actually look at compat_flags.  This
will mess any attempt to use compat flags up.  The fix is obvious.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -1842,7 +1842,7 @@ BTRFS_SETGET_STACK_FUNCS(super_num_devices, struct btrfs_super_block,
 BTRFS_SETGET_STACK_FUNCS(super_compat_flags, struct btrfs_super_block,
 			 compat_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_compat_ro_flags, struct btrfs_super_block,
-			 compat_flags, 64);
+			 compat_ro_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_incompat_flags, struct btrfs_super_block,
 			 incompat_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_csum_type, struct btrfs_super_block,