usb: renesas_usbhs: Add support for R-Car E2

This patch adds a compatible string to support for R-Car E2.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>" in patch 2
Signed-off-by: Felipe Balbi <balbi@ti.com>