qed/qed_sriov: guard against NULL derefs from qed_iov_get_vf_info

[ Upstream commit 25143b6a ]

We have to make sure that the info returned by the helper is valid
before using it.

Found by Linux Verification Center (linuxtesting.org) with the SVACE
static analysis tool.

Fixes: f990c82c ("qed*: Add support for ndo_set_vf_trust")
Fixes: 733def6a ("qed*: IOV link control")
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>