arm64: defconfig: Enable Renesas MTU3a PWM config

Enable PWM config for Renesas MTU3a PWM as it is populated on
RZ/{G2L, LC, UL} and RZ/V2L SMARC EVKs.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230703132706.355237-1-biju.das.jz@bp.renesas.com


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