mmc: sunxi: add support for automatic delay calibration

A64 and H6 support automatic delay calibration and Linux driver uses it
instead of hardcoded delays. Add support for it to u-boot driver.

Fixes eMMC instability on Pinebook

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Cc: Vagrant Cascadian <vagrant@debian.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>