mali_kbase: add asynchronous power control (APC) support

Introduce KBASE_IOCTL_APC_REQUEST, which does asynchronous GPU power
control work on a realtime kernel thread called mali_apo_thread. GPU
will stay powered on based on the requested wake duration capped by a
pre-defined maximum duration.

mali_apc_thread is bound to little cores.

Bug: 170337464
Test: systrace and latency sensitive workload
Signed-off-by: Yiwei Zhang <zzyiwei@google.com>
Change-Id: Ia64977095dfb31db93ceaeb2b02ce436c41408d9