arm64: dts: renesas: r8a7795: salvator-xs: enable usb2_phy3 node

This patch enables usb2_phy3 node for r8a7795 with Salvator-XS.
You must change the SW31 to OFF-OFF-ON-ON-ON-ON on the board.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>