regulator: Rename set_voltage_sel callback function name to *_sel

This change improves readability.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

diff --cc drivers/regulator/tps65910-regulator.c
Simple merge

diff --cc drivers/regulator/tps65912-regulator.c
Simple merge