Fix interrupts delivery on ThunderX for VF IDs beyond 8

SR-IOV devices usually use Alternative Routing ID (ARI).
In that case slot/device is always assumed to be 0 and
function/identifier is extended to 8 bits.

Fix interrupts delivery to VF IDs beyond 8 by using a correct
DevID if ARI is enabled.

Reviewed by: jhb, wma
Obtained from: Semihalf
Sponsored by: Cavium
Differential Revision: https://reviews.freebsd.org/D5855