Mainline Linux now has basic s500/roseapplepi support, so switch to that to
get rid of the dependency on gcc7. Add two patches for the dts / fix that
didn't make it for kernel 5.7.
The mainline kernel does not yet have support for the mmc interface, so
change to initramfs for now. Patches for mmc support have been posted
recently, so this can be reverted once they show up in a stable kernel:
https://lore.kernel.org/lkml/cover.1593124368.git.cristian.ciocaltea@gmail.com/
The owl serial port is called ttyOWLn in mainline, so adjust the bootargs to
match. Also drop the unneeded execute permission on uEnv.txt.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
