devices: make more classes derive from BasicPioDevice

devices: make more classes derive from BasicPioDevice
A couple of devices that have single fixed memory mapped regions
were not derived from BasicPioDevice, when that's exactly
the functionality that BasicPioDevice provides.  This patch
gets rid of a little bit of redundant code by making those
devices actually do so.

Also fixed the weird case of X86ISA::Interrupts, where
the class already did derive from BasicPioDevice but
didn't actually use all the features it could have.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>