ANDROID: GKI: enable CONFIG_SUN4I_TIMER

Allwinner's SoC timer driver (timer-sun4i.c) has to be built-in rather
than modularized for the following limitations in linux timer framework:
1. tick broadcast installed by insmod cannot switch to oneshot mode
   correctly
2. cpus cannot enter cpuidle state due to the issue above.
3. rcu warnings will appear if we forcibly re-enable tick-broadcast
   for each cpu when new tick broadcast device is installed by insmod
   (timer-sun4i.c in our case)

Bug: 173667601
Change-Id: If077db348c027ec02549e25eee3e17c2cc429644
Signed-off-by: Martin Wu <wuyan@allwinnertech.com>