arm64: defconfig: add imx8qxp support

Enable basic drivers for imx8qxp booting up support:
SCU firmware, Mailbox(MU), SCU Power Domain/Pinctrl/Clock,
Uart, MMC, FEC.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>