With gcc >= 6.0, qede base driver fails to build with:
drivers/net/qede/base/ecore_cxt.c: In function 'ecore_cdu_init_common':
cc1: error: left shift of negative value [-Werror=shift-negative-value]
Since the base drivers are untouchable, work around by disabling
the warning.
Fixes: ec94dbc57362 ("qede: add base driver")
Signed-off-by: Panu Matilainen <pmatilai@redhat.com>