fix i386 build with CPU_ELAN (LINT for instance) after r331878
x86/cpu_machdep.c now needs to include elan_mmcr.h when CPU_ELAN is set.
While here, also remove the now unneeded inclusion of isareg.h in i386
and amd64 vm_machdep.c.
Reported by: lwhsu
MFC after: 14 days
X-MFC with: r331878