virtio_blk: fix snprintf truncation compiler warning

Commit 4e040052 ("virtio-blk: support polling I/O") triggers the
following gcc 13 W=1 warnings:

drivers/block/virtio_blk.c: In function ‘init_vq’:
drivers/block/virtio_blk.c:1077:68: warning: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 7 [-Wformat-truncation=]
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                                                                    ^~
drivers/block/virtio_blk.c:1077:58: note: directive argument in the range [-2147483648, 65534]
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                                                          ^~~~~~~~~~~~~
drivers/block/virtio_blk.c:1077:17: note: ‘snprintf’ output between 11 and 21 bytes into a destination of size 16
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is a false positive because the lower bound -2147483648 is
incorrect. The true range of i is [0, num_vqs - 1] where 0 < num_vqs <
65536.

The code mixes int, unsigned short, and unsigned int types in addition
to using "%d" for an unsigned value. Use unsigned short and "%u"
consistently to solve the compiler warning.

Cc: Suwan Kim <suwan.kim027@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312041509.DIyvEt9h-lkp@intel.com/


Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20231204140743.1487843-1-stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>