ARM: multi_v7_defconfig: Enable USB3503 driver

The Odroid U3 (Exynos 4412 based) for instance needs this driver,
otherwise its USB hub will not come up.

Also selecting it as built-in to allow booting from USB without
an initrd/initramfs.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>