sunxi: revert disabling of features

In January some commits were introduced to mitigate the U-Boot image
size issues we encountered on sunxi builds.
Now with the MMC environment removed we can bring them back, as we
practically don't have a size limit anymore.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>