ARM: pxa168/gplugd: get rid of mfp-gplugd.h

Move definitions from mfp-gplugd.h to mfp-pxa168.h as they aren't
gplugD specific.

Signed-off-by: Tanmay Upadhyay <tanmay.upadhyay@einfochips.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>