gpio: palmas: Add support for Palmas GPIO

Add gpio driver for TI Palmas series PMIC. This has 8 gpio which can
work as input/output.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>