x86: Templatize the IntMasterPort.

x86: Templatize the IntMasterPort.

This makes the IntMasterPort usable with any class, making it possible
to avoid inheriting from IntDevice.

It also makes IntMasterPort inherit directly from QueuedMasterPort,
skipping over MessageMasterPort.

Change-Id: I9d218556c838ea567ced5f6fa4d57a3ec9d28d31
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20821
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>