Fix 32-bit build

Fix building on 32-bit machines (ARMv7)
Update for v9 of QEMU patch.

Handling VHOST_SET_VRING_KICK, VHOST_SET_VRING_CALL:
 - in msg.u64, bits 0-7 contain the vring index
 - in msg.u64, bit 8 designates invalid fd

When receiving invalid KICK fd - start polling.