udev: Bring meta-mentor-staging changes in line with upstream

Since these files were created there have been several changes to
the upstream versions in poky that we are not getting since this
file completely overrides the upstream.  Rework these files to
clearly spell out what our differences are to make them easier
to maintain moving forward.

Signed-off-by: Drew Moseley <drew_moseley@mentor.com>
Merge pull request #209 from drewmoseley/fix-udev-mount-scripts

Fix udev mount scripts