regulator: raa215300: Add const definition

Add const definition to the initialized local variable name to avoid
overriding. Also the second parameter in strscpy is const char * instead of
char *.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230816135550.146657-3-biju.das.jz@bp.renesas.com


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