Add selftest file for the link layer tests of a NIC driver.
Test for auto-negotiation is added.
Add LinkConfig class for changing link layer configs.
Selftest makes use of ksft modules and ethtool.
Include selftest file in the Makefile.
Signed-off-by: Mohan Prasad J <mohan.prasad@microchip.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>