Fix the real problem with missing UFS/MSDOSFS labels on the
FreeBSD/arm builds. The problem stems from the loader.rc file
not existing, as well as geom_label not being loaded at boot.

For now, add the geom_label_load entry to loader.conf, and
symlink loader.rc.sample to loader.rc, both of which allowed
my BeagleBone Black to boot fine with a UFS label reference in
fstab(5).

MFC after: 3 days
X-MFC-Before: 10.2-BETA1
Sponsored by: The FreeBSD Foundation