drivers/power/qpnp-charger.c: fix charging issues with non-Oppo chargers

1. refactor the current limiting code to use existing temperature sensing
   capability rather than some arbitrary 1 minute loop

2. removed all current check loops below 900mA. Due to inaccurate ADC input
   readings, some non-Oppo wall chargers are mis-identified and their charging
   capabilities severely limited by the over protective driver

USB data port charging are unaffected by these changes

Change-Id: Id888a25b02b99556d29156520e01d21f7a487168
Signed-off-by: Paul Reioux <reioux@gmail.com>
Merge "drivers/power/qpnp-charger.c: fix charging issues with non-Oppo chargers" into kk4.4