Add mlabel as GPLv2 alternative for dosfslabel

The dosfstools were downgraded to v2.11 after switching to the nogplv3 image. This version of dosfstools has no partition labeling tool.

[addition for 746-001602]

This is a follow up to the !33 (merged). I overlooked that fatlabel is also used under a different name in install-scripts/fnginstall-common.sh script.