net/i40e: downgrade error log

When receiving the unsupported AQ messages, it's taken as an
error. It's not appropriate and triggers too much unnecessary print.

This commit is similar to
commit e130425300b0 ("net/i40e: downgrade unnecessary error log")
which made the same change for the PF instance.

Fixes: ae19955e7c86 ("i40evf: support reporting PF reset")
Cc: stable@dpdk.org
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Xiaolong Ye <xiaolong.ye@intel.com>