huawei_battery: allow disabling BATT_ID and RESISTANCE_ID RPC

u8815 does not support this and it's very spammy.
hw_backlight: restore code for u8815

Necessary to fix an occasional ~24 second screen on delay on u8815.
I assume this is somewhere around the amount of time it takes for
Android to dim the screen before falling asleep.
Merge branch 'master' into jb-mr2