This patch implements a better way to handle multiple SoC's and adds
Intel Merrifield support to gpio-langwell.

It was based on previous work from Ning Li <ning.li@intel.com>
Signed-off-by: NDavid Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: NFei Yang <fei.yang@intel.com>
Signed-off-by: NNing Li <ning.li@intel.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>