btrfs: change btrfs_csum_final result param type to u8

csum member of struct btrfs_super_block has array type of u8. It makes
sense that function btrfs_csum_final should be also declared to accept
u8 *. I changed the declaration of method void btrfs_csum_final(u32 crc,
char *result); to void btrfs_csum_final(u32 crc, u8 *result);

Signed-off-by: Domagoj Tršan <[email protected]>
[ changed cast to u8 at several call sites ]
Signed-off-by: David Sterba <[email protected]>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index d4d8b7e..4910803 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -120,7 +120,7 @@ static int check_compressed_csum(struct inode *inode,
 
 		kaddr = kmap_atomic(page);
 		csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE);
-		btrfs_csum_final(csum, (char *)&csum);
+		btrfs_csum_final(csum, (u8 *)&csum);
 		kunmap_atomic(kaddr);
 
 		if (csum != *cb_sum) {