ARM: multi_v7_defconfig: Drop useless CONFIG_USB_RCAR_PHY=y

The Renesas R-Car (Gen1) USB PHY driver (which is being removed) does
not support DT, and is thus useless in a generic ARM multi-platform
kernel.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>