irqchip: bcm7120-l2: Use gc->mask_cache to simplify suspend/resume functions

The cached value already incorporates irq_fwd_mask, and was saved the
last time an IRQ was enabled/disabled.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lkml.kernel.org/r/1415342669-30640-11-git-send-email-cernekee@gmail.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>