Partial rewrite of SDHOST driver to use DMA for data transfer

This reverts the microSD performance to that seen with the SDHCI controller.

Benchmarks on Pi Zero W (ARM1176JZF-S):
  SDHCI:      23.8 MB/s
  SDHOST PIO:  1.9 MB/s
  SDHOST DMA: 24.4 MB/s

Benchmarks on Pi Zero 2W (Cortex-A53):
  SDHCI:      23.8 MB/s
  SDHOST PIO:  8.6 MB/s
  SDHOST DMA: 24.4 MB/s
8 jobs for SDIO in 6 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Static Analysis
passed #42627
cross
gitattributes

00:00:01

passed #42628
cross
gitignore

00:00:00

passed #42631
cross
head_log

00:00:00

passed #42633
cross
head_whitesp

00:00:00

passed #42629
cross
license

00:00:00

passed #42632
cross
makefile

00:00:00

passed #42630
cross
versionnum

00:00:00

 
  Cleanup
passed #42634
cross
cleanup

00:00:00