regulator: raa215300: Update help description

Add module description to the help section and update the existing
help description.

Reported-by: Pavel Machek <pavel@denx.de>
Closes: https://lore.kernel.org/all/ZN3%2FSjL50ls+3dnD@duo.ucw.cz/


Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230818141815.314197-4-biju.das.jz@bp.renesas.com


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