selftests: drivers: hw: replace counter upper limit with UINT32_MAX in rmon test

selftests: drivers: hw: replace counter upper limit with UINT32_MAX in rmon test

The ethtool_rmon.sh script checks that the number of packets sent /
received during a test matches the expected value with a 1% tolerance.

Since in the next patches this test will gain the capability to also be
run on systems with a single interface where the traffic generator is
accesible through ssh, use the UINT32_MAX as the upper limit. This is
necessary since the same interface will be used also for control traffic
(the ssh commands) as well as the mausezahn generated one.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20260330152933.2195885-7-ioana.ciornei@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>