pinctrl: renesas: r8a77965: Optimize pinctrl image size for R8A774B1

This driver supports both RZ/G2N and R-Car M3-N SoCs.
Optimize pinctrl image size for RZ/G2N, when support for R-Car M3-N
(R8A77965) is not enabled.

Based on the simialr patch on Linux.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>