fstab: Mount boot and config, use label to detect disks
The naming of mmcblk0 vs mmcblk1 is not stable (and not supposed to be by the kernel), disabling of one external mmc in the devicetree moves mmc1 to mmc0.
This adds and fstab to mount the config partition and the boot partition by label.
Also adapts gf-prepare-kernel to detect the boot partition by label and use the hardcoded paths only as fallback.
Moves fng-install files from mx6 one level up as those should get valid for nallino (mx6ull) too.
Not sure what to do with the root= kernel parameter. It is supposed to work with an PARTUUID but I didn't got this working until now.
BCS 746-000085