arm64: defconfig: enable I2C and DW MMC controller on rockchip platform

I2C and MMC are very basic modules for a board to bootup, as I2C always
used to configure PMIC and MMC devices often used to store filesytem.
So enable them here to let the rockchip based arm64 boards can bootup.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>