f2fs: fix typo

Fix typo and some grammatical errors.

The words "filesystem" and "readahead" are being used without the space treewide.

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index a441ba3..fecebdb 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -32,7 +32,7 @@
 	struct f2fs_stat_info *si = F2FS_STAT(sbi);
 	int i;
 
-	/* valid check of the segment numbers */
+	/* validation check of the segment numbers */
 	si->hit_ext = sbi->read_hit_ext;
 	si->total_ext = sbi->total_hit_ext;
 	si->ndirty_node = get_pages(sbi, F2FS_DIRTY_NODES);
@@ -152,7 +152,7 @@
 	si->base_mem += NR_DIRTY_TYPE * f2fs_bitmap_size(TOTAL_SEGS(sbi));
 	si->base_mem += f2fs_bitmap_size(TOTAL_SECS(sbi));
 
-	/* buld nm */
+	/* build nm */
 	si->base_mem += sizeof(struct f2fs_nm_info);
 	si->base_mem += __bitmap_size(sbi, NAT_BITMAP);