sunxi: disable direct MMC environment

Since the dawn of time for the Allwinner support in mainline U-Boot
we store the environment to the SD card and write directly at
544KB from the beginning of the device. This leads to problems when
the U-Boot proper image grows beyond 504KB and eventually overlaps.
With one release of having the environment preferably in a FAT
partition, let's now turn off the MMC variant fallback, so we get back
all the space we need to implement features.

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

env/Kconfig

@@ -152,7 +152,6 @@ config ENV_IS_IN_MMC
 	bool "Environment in an MMC device"
 	depends on !CHAIN_OF_TRUST
 	depends on MMC
-	default y if ARCH_SUNXI
 	default y if ARCH_EXYNOS4
 	default y if MX6SX || MX7D
 	default y if TEGRA30 || TEGRA124