Add a helper function that allow regulator consumers to allow low-level
HW access, in order to enable/disable regulator in atomic context.

The use-case for RZ/G2L SoC is to enable VBUS selection register based
on vbus detection that happens in interrupt context.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20240616105402.45211-4-biju.das.jz@bp.renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>