mk_mmc.sh: cleanup fdtfile

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
mk_mmc.sh: combine these

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
mk_mmc.sh: optimize these

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
mk_mmc.sh: combine these

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
mk_mmc.sh: use bootpart

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>