bio: change some signed vars to unsigned

This is just a cleanup patch to silence a static checker warning.

The problem is that we cap "nr_iovecs" so it can't be larger than
"UIO_MAXIOV" but we don't check for negative values.  It turns out this is
prevented at other layers, but logically it doesn't make sense to have
negative nr_iovecs so making it unsigned is nicer.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/bio.c

@@ -337,7 +337,7 @@ static void bio_fs_destructor(struct bio *bio)
  *	RETURNS:
  *	Pointer to new bio on success, NULL on failure.
  */
-struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
+struct bio *bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)
 {
 	struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
 
@@ -365,7 +365,7 @@ static void bio_kmalloc_destructor(struct bio *bio)
  *   %__GFP_WAIT, the allocation is guaranteed to succeed.
  *
  **/
-struct bio *bio_kmalloc(gfp_t gfp_mask, int nr_iovecs)
+struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)
 {
 	struct bio *bio;
 
@@ -696,7 +696,8 @@ static void bio_free_map_data(struct bio_map_data *bmd)
 	kfree(bmd);
 }
 
-static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
+static struct bio_map_data *bio_alloc_map_data(int nr_segs,
+					       unsigned int iov_count,
 					       gfp_t gfp_mask)
 {
 	struct bio_map_data *bmd;