uboot-imx6: bump to 2020.01 and refresh patches

Update U-Boot to latest release, remove `100-wandboard-enable-fit.patch`
as FIT support was added in commit 5b8585825128 ("wandboard: Add FIT
image support").

Rework `110-mx6cuboxi-mmc-fallback.patch` into two patches as there was
new config option `CONFIG_SPL_FORCE_MMC_BOOT` added upstream which
should provide the same functionality as the previous patch hunk.

Moving Apalis towards generic distro_bootcmd.

Cc: Vladimir Vid <vladimir.vid@sartura.hr>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Koen Vandeputte <koen.vandeputte@ncentric.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>