ARM: plat-nomadik: move NMK_GPIO_PER_CHIP into gpio-nomadik.h

Move NMK_GPIO_PER_CHIP to gpio-nomadik.h and define it with a
shift operator.

Signed-off-by: Patrice Chotard <patrice.chotard@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>