hwmon: epm_adc: Update sysfs channel names

Update the channel name listing from ADS to PSOC.
The newer EPM uses PSOC, therefore update the string
names to accurately reflect the underlying interface
to measure the ADC for EPM.

Change-Id: I89931c9cffe91ff1846c91a85629c7b5d494bf57
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>