ARM: nmk: update GPIO chained IRQ handler to entry/exit functions

This patch updates the Nomadik gpio chained IRQ handler to use the
chained IRQ enter/exit functions in order to function correctly on
primary controllers with different methods of flow control.

Cc: Rabin Vincent <rabin@rab.in>
Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>