dev: Rename VirtIO PCI debug flag

dev: Rename VirtIO PCI debug flag

Rename VIOPci -> VIOIface to avoid having a separate flag for the MMIO
interface.

Change-Id: I99f9210fa36ce33662c48537fd3992cd9a69d349
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sudhanshu Jha <sudhanshu.jha@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Rekai Gonzalez Alberquilla <rekai.gonzalezalberquilla@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2324
Reviewed-by: Weiping Liao <weipingliao@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>