More clearly differentiate MVIC vs. APIC timer code, and use new APIC
accessors in include/drivers/loapic.h. Remove extraneous comments, and
other light cleanup work.
This driver is in need of a serious overhaul -- despite appearing to
have support for TICKLESS_KERNEL and DEVICE_POWER_MANAGEMENT, bitrot
has taken its toll and the driver will not build with these enabled.
These should be removed or made to work... but not in this patch.
Old x2APIC-related accessors in kernel_arch_func.h are eliminated.
Signed-off-by: Charles E. Youse <charles.youse@intel.com>