selftests: net: Use XFAIL for operations not supported by the driver

Check if veth pair was created and if yes, xfail on setting IP address
logging an informational message.
Use XFAIL instead of SKIP for unsupported ethtool APIs.

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240821171903.118324-4-jain.abhinav177@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>