hwmon: qpnp-adc-voltage: Show ADC code in hex format

Update the raw code shown for VADC while printing the buffer
in hex format instead of decimal format to maintain the
format that is in the register.

Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
Change-Id: I57f39e1d32925a51ca2bc6e848cc897caf565c6c