rockchip: fix the SD card detection on NanoPi R6C/R6S

rockchip: fix the SD card detection on NanoPi R6C/R6S

This patch backport a fix for the SD card detection on NanoPi R6c/R6S
from upstream commit https://github.com/torvalds/linux/commit/95147bb42bc163866fc103c957820345fefa96cd

Signed-off-by: Antonio Flores <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/18553
Signed-off-by: Robert Marko <[email protected]>
(cherry picked from commit 5c83301107d238e6c3ea829ae09d87396da0b4db)
Link: https://github.com/openwrt/openwrt/pull/19138
Signed-off-by: Hauke Mehrtens <[email protected]>