power: pm8921-charger: remove old workarounds

PMIC8921 revision 1.0 and 1.1 are no longer supported by software.

Remove the applicable workarounds from the driver.

Change-Id: I8c99fcbbf2f7229728236ae1059f4c9cb8dbb065
Signed-off-by: David Keitel <dkeitel@codeaurora.org>