testing: net-drv: add a driver test for stats reporting

Add a very simple test to make sure drivers report expected
stats. Drivers which implement FEC or pause configuration
should report relevant stats. Qstats must be reported,
at least packet and byte counts, and they must match
total device stats.

Tested with netdevsim, bnxt, in-tree and installed.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>