Reworking the initial filesystem image #34

This PR does the following:

• board/MynaPlayer odyssey: remove rauc partition from genimage, and reworked the overlay filesystem creation.
  • The rauc partition was not needed seeing we make use of a large overlay filesystem. Remove it.
  • The fstab is now an empty file, so we avoid the original buildroot one.
  • The rauc-marking-good.service now runs mkdir -p to create the /rauc directory before it marks the slot good.
  • Also, the post-image script was modified to no longer create filesystems using fallocate. This was honestly dirty and added one more dependency in building MynaPlayer.
  • Genimage now takes care of creating the overlay filesystem instead.
• board/MynaPlayer odyssey: remove defined partition types in genimage template.
  • This was ignored previously when the disk was set to gpt partitioning scheme.
  • It now enforces hybrid mbr, which stm32mp1 cannot handle, so lets remove the type.
• board/MynaPlayer odyssey: tweak pre-init script.
  • This is required so that the overlayfs partition is changed to p5 instead of p6, since the rauc partition was removed.

Reworking the initial filesystem image