net/i40e: remove empty queue stats mapping set devops

net/i40e: remove empty queue stats mapping set devops

This driver was inserting its own stub for queue_stats_mapping which
did nothing but cause this device to return a different errno
than every other device driver.  All devices that don't implement
queue stats mapping should return the same error.

Maybe the plan originally was to implement something, if that
ever happens, just put in the right code.

Fixes: 4861cde46116 ("i40e: new poll mode driver")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>