regulator: spmi: Add support for ULT LV_P50 and ULT P300

The ULT LV_P50 shares the same configuration as the other ULT LV_Pxxx
and the ULT P300 shares the same as the other ULT Pxxx.

These two regulator types are found on PM8950 and its variants.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210225213514.117031-1-konrad.dybcio@somainline.org
Signed-off-by: Mark Brown <broonie@kernel.org>