ANDROID: gic-v3: Export gic_v3_resume() for vendor GIC enhancements

syscore ops in gic-v3 takes care of invoking gic_v3_resume() when
exiting from "deep" suspend. However for "s2idle" suspend syscore
ops will not get invoked.

Vendor modules can register for s2idle notifications and
invoke gic_v3_resume() when the first cpu is waking up from s2idle.

Bug: 279879797
Change-Id: Ifd48d676a5bc907eb957c2002934e18bd1c9c095
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Shreyas K K <quic_shrekk@quicinc.com>