power: pm8921-charger: get rid of using LPM

The LPM is causing a lot of regression on various test cases
1. Writes to charger have become complex
2. There is uncertainty about whether battery insertion/removal could be
detected reliably.

LPM was introduced to prevent lockups from happening when the charger
was running in hw based clock switching while it was suspended. UVLO
lockups were not seen if the charger was running from 19.2Mhz.

Instead activate LPM mode only while the system is suspended and always
force 19.2Mhz when not suspended. This way we avoid the complexities
with writes, can detect battery insertion/removal as long as the system
is not suspended and more importantly fix the UVLO issue since we will
never be running in hw clk switching mode.

Change-Id: I94510311b503c21ec659a96982010435abdbcfaf
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>