drivers/gpio: add missing GENERIC_HARDIRQ dependency

The VIA VX855/VX875 GPIO and RDC R-321x GPIO support drivers select
MFD_CORE which itself depends on GENERIC_HARDIRQ support.
So add this dependency to these two drivers as well to prevent
selection of MFD_CORE.

Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>