rockchip: board: Add minimal generic RK3588S/RK3588 board

Add a minimal generic RK3588S/RK3588 board that only have eMMC and SDMMC
enabled. This defconfig can be used to boot from eMMC or SD-card on most
RK3588S/RK3588 boards that follow reference board design.

Also fix the alphabetical order of RK3588 boards listed in Makefile and
documentation.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
diff --git a/doc/board/rockchip/rockchip.rst b/doc/board/rockchip/rockchip.rst
index c35f256..93aceb1 100644
--- a/doc/board/rockchip/rockchip.rst
+++ b/doc/board/rockchip/rockchip.rst
@@ -121,12 +121,13 @@
      - Edgeble Neural Compute Module 6A SoM - Neu6a (neu6a-io-rk3588)
      - Edgeble Neural Compute Module 6B SoM - Neu6b (neu6b-io-rk3588)
      - FriendlyElec NanoPC-T6 (nanopc-t6-rk3588)
+     - Generic RK3588S/RK3588 (generic-rk3588)
      - Pine64 QuartzPro64 (quartzpro64-rk3588)
-     - Turing Machines RK1 (turing-rk1-rk3588)
      - Radxa ROCK 5A (rock5a-rk3588s)
      - Radxa ROCK 5B (rock5b-rk3588)
      - Rockchip Toybrick TB-RK3588X (toybrick-rk3588)
      - Theobroma Systems RK3588-SBC Jaguar (jaguar-rk3588)
+     - Turing Machines RK1 (turing-rk1-rk3588)
      - Xunlong Orange Pi 5 (orangepi-5-rk3588s)
      - Xunlong Orange Pi 5 Plus (orangepi-5-plus-rk3588)