regulator: qcom_smd: add get_voltage to MP5496

Add the get_voltage OP to MP5496 ops using the generic rpm_reg_get_voltage.

Signed-off-by: Robert Marko <robimarko@gmail.com>
Link: https://lore.kernel.org/r/20220604193300.125758-1-robimarko@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>