gcc 5 supports a new logical-not-parentheses warning which
ixgbe_common.c triggers, causing build failure with -Werror.
Since this source must not be modified, silence the warning instead.
Signed-off-by: Panu Matilainen <pmatilai@redhat.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>