ARM: multi_v7_defconfig: Replace USB_RCAR_GEN2_PHY by PHY_RCAR_GEN2

The legacy-only USB_RCAR_GEN2_PHY driver was replaced by the DT-only
PHY_RCAR_GEN2 driver.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>