boards: renesas: Add PWM support for Renesas RA6, RA4, RA2

Add pinctrl & node of pwm driver for these board:
ek_ra2a1, ek_ra4e2, ek_ra4m2, ek_ra4m3, ek_ra4w1,
ek_ra6e2, ek_ra6m1, ek_ra6m2, ek_ra6m3, ek_ra6m4,
ek_ra6m5, fpb_ra6e1, fpb_ra6e2.

Signed-off-by: Danh Doan <danh.doan.ue@bp.renesas.com>