iio: qcom-rradc: Update reading battery ID channel

The battery ID channel on the RRADC can be disabled
during initialization. Therefore update the sequence
to enable the channel before enabling the trigger and
continuous mode. After reading the battery ID result
from the RRADC controller, disable the trigger
and disable the channel after conversion request.

CRs-Fixed: 2023991
Change-Id: I461e04175ae351312b68771ef85cd928d5c0e4b1
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>