langwell_gpio: add support for whitney point

In this case the logic is very similar but the IRQs are not exposed and
the device is not picked up via PCI

Based on a separate internal whitney point driver by Yin Kangkai.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Yin Kangkai <kangkai.yin@intel.com>
Cc: Alek Du <alek.du@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>