pinctrl: renesas: rzg2l: Validate power registers for SD and ETH

On RZ/V2H(P) SoC, the power registers for SD and ETH do not exist,
resulting in invalid register offsets.  Ensure that the register offsets
are valid before any read/write operations are performed.  If the power
registers are not available, both SD and ETH will be set to '0'.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com> # on RZ/G3S
Link: https://lore.kernel.org/r/20240530173857.164073-7-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>