power: qpnp-charger: remove incorrect write to TEST_SMBC_MODES

The TEST_SMBC_MODES register controls the duty cycle of the
SMBB_BUCK peripheral. Remove the unecessary write. Instead
the devicetree propert qcom,duty-cycle-100p should be defined
to enable the 100% duty cycle.

Change-Id: Ib6811ae6b85d7e61054e5a7240c9a20b22822a3c
Signed-off-by: David Keitel <dkeitel@codeaurora.org>