Btrfs: subpage-blocksize: Rate limit scrub error message

btrfs/073 invokes scrub ioctl in a tight loop. In subpage-blocksize
scenario this results in a lot of "scrub: size assumption sectorsize !=
PAGE_SIZE " messages being printed on the console. To reduce the number
of such messages this commit uses btrfs_err_rl() instead of
btrfs_err().
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/scrub.c

@@ -3856,7 +3856,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
 
 	if (fs_info->chunk_root->sectorsize != PAGE_SIZE) {
 		/* not supported for data w/o checksums */
-		btrfs_err(fs_info,
+		btrfs_err_rl(fs_info,
 			   "scrub: size assumption sectorsize != PAGE_SIZE "
 			   "(%d != %lu) fails",
 		       fs_info->chunk_root->sectorsize, PAGE_SIZE);