[ARM] pxa: removing dead ARCH_GUMSTIX_ORIG

ARCH_GUMSTIX_ORIG doesn't exist in Kconfig, therefore removing all
references for it from the source code.

Signed-off-by: Christoph Egger <siccegge@cs.fau.de>
Acked-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>