[PATCH] dts64: mt7622: fix slow sd card access

[Frank Wunderlich]

I guess issue is caused by incompatible setting in uboot,but have not found which exactly so i handled it like emmc.

If patch is ready to be applied please add 

Cc: stable at vger.kernel.org

because all kernel versions are affected (tested at least in 5.4 and 5.9). If i need to create a v2,i will add it

@sean/ryder/wenbin can you tell me if sd on mt7622/bpi-r64 is maybe capable of hs400?
regards Frank