dt-bindings: clock: renesas,rzg2l-cpg: Update description for #reset-cells

dt-bindings: clock: renesas,rzg2l-cpg: Update description for #reset-cells

For the RZ/G2L and similar SoCs, the reset specifier is the reset number
and not the module number. Reflect this in the description for the
'#reset-cells' property.

Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240606161047.663833-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>