thermal: adc_tm: Update channel assignments for PM8150B 1.0

BTM channels CH_0 and CH_1 on PM8150B on 1.0 are reserved.
Therefore assign any BTM channels from CH_2 onwards
for PM8150B 1.0.

Change-Id: I3bb7a3d60f6a8502a7e6561b8258173e0317a4d6
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>