Add initial support for SDHCI controller in RK3528.

Only MMC Legacy and MMC High Speed (52MHz) mode is supported after this,
more work is needed to get the faster HS200/HS400/HS400ES modes working.

Variant tap and delay num is copied from vendor Linux tag
linux-6.1-stan-rkr5.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>