regulator: s5m8767: Remove max_vol parameter from s5m8767_convert_voltage_to_sel

It looks pointless to pass max_vol to s5m8767_convert_voltage_to_sel().
Compare selected voltage to desc->max is enough to ensure selected voltage
is in supported range.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>