nyan*: Enable SD card power in initialization.

After a warm reboot, Tegra SD card reader must be re-initialized by cycling its
power GPIO and VDD_SDMMC.  Previous loader (ex, Coreboot) should clear the power
settings, and depthcharge MMC module will set GPIO and VDD starting to access SD
card.

BUG=chrome-os-partner:27053
BRANCH=nyan
TEST=emerge-nyan coreboot depthcharge chromeos-bootimage
     On a Nyan/Norrin DEV mode, insert Sandisk class 10 SD card,
     first boot eMMC system, mount SD card, run "reboot" command,
     press Ctrl-U in DEV screen to boot SD card (success).
     Run "crossystem recovery_request=1" then "reboot" (success).

Change-Id: I40b251d3400cafac810494ba3627142f10de5baa
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/196783
Reviewed-by: Gabe Black <gabeblack@chromium.org>
Tested-by: Andrew Bresticker <abrestic@chromium.org>
5 files changed