vhost_kern: set the proper type of constants
vhost_kern: set the proper type of constants

VHOST_ACCESS_* and VHOST_IOTLB_* constants are assigned to c_uchar
fields and VHOST_IOTLB_MSG to a c_int field.

Let's set the proper types to avoid casts when assigning them.

Signed-off-by: Stefano Garzarella <6f3dd2004310421c0dda1107f4857e62a774d5df@redhat.com>

rust-vmm/vhost