fix(rpi3): initialize SD card host controller

Add initial configuration parameters for Rasperry Pi 3's sdhost
controller, and then configure and use those parameters.

This change allows warm reboot

fix(rpi3): initialize SD card host controller

Add initial configuration parameters for Rasperry Pi 3's sdhost
controller, and then configure and use those parameters.

This change allows warm reboots of UEFI on Raspberry Pi 3B+ where
existing code often fails with "unknown error". See discussion at:

https://github.com/pftf/RPi3/issues/24

The basic idea is that some initial configuration parameters
(clock rate, bus width) aren't configured into the hardware before
commands start being sent. I suspect that the particular setting
that matters is the "slow card" bit, but the initial clock setting
also seemed wrong to me.

Change-Id: I526def340def143f23f3422f1fc14c12c937ca7f
Signed-off-by: Rob Newberry <robthedude@mac.com>

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rpi3: sdhost: SDHost driver improvement

This commit improves the SDHost driver for RPi3 as following:
* Unblock MMC_CMD(17). Using MMC_CMD(17) is more efficient on
block reading.
* In some low

rpi3: sdhost: SDHost driver improvement

This commit improves the SDHost driver for RPi3 as following:
* Unblock MMC_CMD(17). Using MMC_CMD(17) is more efficient on
block reading.
* In some low probability that SEND_OP_COND might results CRC7
error. We can consider that the command runs correctly. We don't
need to retry this command so removing the code for retry.
* Using MMC_BUS_WIDTH_1 as MMC default value to improve the stability.
* Increase the clock to 50Mhz in data mode to speed up the io.
* Change the pull resistors configuration to gain more stability.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>

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