x86: refactor ->setup_portio_remap() subarch methods

Only NUMAQ has a real ->setup_portio_remap() method, the other
subarchitectures define it but keep it empty.

So mark the vector as NULL, extend the generic code to handle
NULL -setup_portio_remap() entries and remove all the empty
handlers.

Also move the NUMAQ method from the header file into the
 apic driver .c file.

Signed-off-by: Ingo Molnar <mingo@elte.hu>