gpio: rdc321x needs to select MFD_CORE
gpio: rdc321x needs to select MFD_CORE

Fix rdc321x-southbridge build:  GPIO_RDC321X needs to select
MFD_CORE so that the core is built at the same (or higher)
tristate level.

rdc321x-southbridge.c:(.devinit.text+0x6103): undefined reference to `mfd_add_devices'
rdc321x-southbridge.c:(.devexit.text+0xe5f): undefined reference to `mfd_remove_devices'

Signed-off-by: Randy Dunlap <e1d10faa7e2a0c027bf1ff1d20e7fd10154be7ea@oracle.com>
Cc:	Florian Fainelli <73262ad0334ab37227b2f7a0205f51db1e606681@openwrt.org>
Signed-off-by: Samuel Ortiz <0ba86cb3f08bbb861958e54bd3438887adb4263c@linux.intel.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs