fs/block: type signature of major_to_index(int) to major_to_index(unsigned)

The major/minor device numbers are always defined and used as `unsigned'.

Signed-off-by: Yang Zhang <kthreadd@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/genhd.c b/block/genhd.c
index 79b9e32..16ccc0d 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -239,7 +239,7 @@
 } *major_names[BLKDEV_MAJOR_HASH_SIZE];
 
 /* index in the above - for now: assume no multimajor ranges */
-static inline int major_to_index(int major)
+static inline int major_to_index(unsigned major)
 {
 	return major % BLKDEV_MAJOR_HASH_SIZE;
 }