btrfs: fix string and comment grammatical issues and typos

Signed-off-by: Nicholas D Steeves <nsteeves@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 516e19d..b677a6e 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -1939,7 +1939,7 @@
 		/*
 		 * Clear all references of this block. Do not free
 		 * the block itself even if is not referenced anymore
-		 * because it still carries valueable information
+		 * because it still carries valuable information
 		 * like whether it was ever written and IO completed.
 		 */
 		list_for_each_entry_safe(l, tmp, &block->ref_to_list,