rockchip-rk3588/6.11: backport Marcin Juszkiewicz's "FriendlyELEC Nan…

…oPC-T6 improvements" v6 series to fix non-LTS and split LTS version of NanoPC T6

- Marcin Juszkiewicz's series https://lore.kernel.org/all/20240829-friendlyelec-nanopc-t6-lts-v6-0-edff247e8c02@linaro.org/ has landed upstream
  - see torvalds/linux@db1dcbe
  - thus we have 2 separate DTs, one for non-LTS, one for LTS; thus also 2 different Armbian boards (see separate commit)
- drop my own patch that added SPI NOR to the T6, as that is now included in the base DT
- this patch shall be dropped when `6.12-rc1` is released