arm64: dts: renesas: r8a7795: add usb2_phy ch3 device node

This patch adds support for usb3_phy ch3 device node for R-Car H3 ES2.0.

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