MFC r257199, r257200, r257217:

Remove all #include <machine/pmap.h> from arm code. It's already
included by vm/pmap.h, which is a prerequisite for arm/machine/pmap.h
so there's no reason to ever include it directly.

Remove #include <machine/frame.h> from all the arm code that doesn't
really need it. That would be almost everywhere it was included. Add
it in a couple files that really do need it and were previously getting
it by accident via another header.

Remove the last dregs of trapframe_t. It turns out only arm was using
this type, so remove it to make arm code more consistant with other
platforms.

MFC r257199, r257200, r257217:

Remove all #include <machine/pmap.h> from arm code. It's already
included by vm/pmap.h, which is a prerequisite for arm/machine/pmap.h
so there's no reason to ever include it directly.

Remove #include <machine/frame.h> from all the arm code that doesn't
really need it. That would be almost everywhere it was included. Add
it in a couple files that really do need it and were previously getting
it by accident via another header.

Remove the last dregs of trapframe_t. It turns out only arm was using
this type, so remove it to make arm code more consistant with other
platforms.