Add support for the Anbernic RG-ARC S and RG-ARC D devices. These
devices feature the following:
 - Rockchip RK3566 SoC
 - 4 inch 480x640 display (rotated)
 - Goodix multi-touch (ARC D only, untested as I lack the device)
 - 1GB (ARC S) or 2GB (ARC D) of RAM
 - 2 SDMMC slots
 - eMMC (ARC D only)
 - Realtek 8821CS WiFi/Bluetooth
 - External stereo speakers
 - 6 face buttons (A, B, C, X, Y, Z) along with a D-Pad and start and
   select buttons.
 - A PWM vibrator.

Note that the Goodix touchscreen on I2C2 is not defined, as I lack
the necessary hardware to confirm it works correctly with the mainline
driver.
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Link: https://lore.kernel.org/r/20240123212111.202146-5-macroalpha82@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>