sunxi: a523: Add OrangePi 4A defconfig

sunxi: a523: Add OrangePi 4A defconfig

The OrangePi 4A is a typical Raspberry Pi model B sized development
board from Xunlong designed around an Allwinner T527 SoC.

The board has the following features:
- Allwinner T527 SoC
- AXP717B + AXP323 PMICs
- Up to 4GB LPDDR4 DRAM
- micro SD slot
- optional eMMC module
- M.2 slot for PCIe 2.0 x1
- 16 MB SPI-NOR flash
- 4x USB 2.0 type-A ports (one can be used in gadget mode)
- 1x Gigabit ethernet w/ Motorcomm PHY (through yet to be supported GMAC200)
- 3.5mm audio jack via internal audio codec
- HDMI 2.0 output
- eDP, MIPI CSI (2-lane and 4-lane) and MIPI DSI (4-lane) connectors
- USB type-C port purely for power
- AP6256 (Broadcom BCM4345) WiFi 5.0 + BT 5.0
- unsoldered headers for ADC and an additional USB 2.0 host port
- 40-pin GPIO header

Add defconfig for it.

Signed-off-by: Chen-Yu Tsai <wens@kernel.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>