validators: Allow uppercase iface names

validators: Allow uppercase iface names

Predictable interface names for PCI devices on non-zero PCI
domains get assigned (by systemd-udev) names like
enP<bus-number>p<port-number>s<slot-number>f<function-number>,
e.g. enP2p1s0f0, which are currently rejected by our validators.
For PCI domain 0000, the "P<bus-number>" is omitted, resulting
in all lowercase iface names.

Allow uppercase iface names by making the re.match test
case-insensitive.

Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
Change-Id: I2bda550c95737fba57b5916a71a3c3b9df66e22d