The PL061 supports interrupts and those can be wakeup interrupts. We
need to provide support for configuring those interrupts as wakeup
sources.

This patch adds irq_set_wake callback for PL061 so that GPIO interrupts
can be configured as wakeup.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>