rockchip: fix eMMC corruption on NanoPC-T6 with A3A444 chips

rockchip: fix eMMC corruption on NanoPC-T6 with A3A444 chips

Some NanoPC-T6 boards with A3A444 eMMC chips experience I/O errors and
corruption when using HS400 mode. Downgrade to HS200 mode to ensure
stable operation.

Fixes: #18844
Signed-off-by: Grzegorz Sterniczuk <grzegorz@sternicz.uk>
Link: https://github.com/openwrt/openwrt/pull/19398
[Add patch header]
(cherry picked from commit c4586ceae85f7f8eefa08c71d0ef67bb07b5e0cc)
[Merge fixes into patch 121]
Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>
Link: https://github.com/openwrt/openwrt/pull/19926
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>