btrfs: unify types for binary search variables

The variables calculating where to jump next are using mixed in types
which requires some conversions on the instruction level. Using 'u32'
removes one call to 'movslq', making the main loop shorter.

This complements type conversion done in a724f31 ("btrfs: do
unsigned integer division in the extent buffer binary search loop")

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

fs/btrfs/ctree.c

@@ -771,7 +771,7 @@ int btrfs_bin_search(const struct extent_buffer *eb, int first_slot,
 		unsigned long offset;
 		struct btrfs_disk_key *tmp;
 		struct btrfs_disk_key unaligned;
-		int mid;
+		u32 mid;
 
 		mid = (low + high) / 2;
 		offset = p + mid * item_size;