pinctrl: sh-pfc: r8a7795: Change USB3_{OVC,PWEN} definitions

Since the latest datasheet revises the names, this patch changes
the definitions from USB3_{OVC,PWEN} to USB2_CH3_{OVC,PWEN}.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>