arm64: defconfig: allow rk3399-based boards to boot from mmc and usb

Enable additional options necessary to boot rk3399-based boards to
boot from either emmc or usb devices, like the arasan sdhci and its phy
as well as the usb2 phy and general rockchip power-domain support.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>