gpio: dwapb: Add support for next generation of X-Gene SoC

Next generation of X-Gene SoC's GPIO hardware register map is very
similar to DW GPIO. It only differs by a few register addresses.
This patch modifies DW GPIO driver to accommodate the difference
in a few register addresses.

Signed-off-by: Hoan Tran <hotran@apm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>