thermal: mediatek: fix register index error

The index of msr and adcpnp should match the sensor
which belongs to the selected bank in the for loop.

Fixes: b7cf0053

 ("thermal: Add Mediatek thermal driver for mt2701.")
Signed-off-by: Michael Kao <michael.kao@mediatek.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>