power: pm8921-charger: force 19.2Mhz clock before accessing registers

The charger was observed to be in locked up state upon booting up. The
initialization time configurations were being ignored causing charging
to not happen.

Fix this by forcing the charger to run from 19.2Mhz clock prior to
accessing any charger registers. This made the charger come out of the
locked up state and accept writes to it.

Change-Id: I0d86c328d4c7022a3bd46c62cb28b12318053f74
CRs-Fixed: 372383
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>