ARM: 6099/1: nomadik-gpio: fix mask/unmask

Mask/unmask should modify the interrupt mask register (RIMSC
and FIMSC) not the wakeup mask registers (RWIMSC and FWIMSC).

Acked-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>