uefi: net: Ignore device paths which are subpaths of already seen devices.

Some devices have sub devices which have a simple network protocol installed
on them, but are not actually functional network devices and are apparently
instead places to hold ipv4 and ipv6 configuration information. Gigaboot deals
with this by comparing device paths and ignoring any devices which are
strictly subpaths of the last device which was successfully recognized. This
is an imperfect check since it relies on the order things are returned in, and
it would also be nice to better understand where these extra devices are coming
from, what they're for, and how they're officially supposed to be handled.
Absent that, this avoids having a bunch of network devices hanging around that
don't actually work.

Change-Id: I01179d2b452c964a80dd101aa9b6e3519518145e
1 file changed