ibmvnic: fix: NULL pointer dereference.

The error is due to dereference a null pointer in function
reset_one_sub_crq_queue():

if (!scrq) {
    netdev_dbg(adapter->netdev,
               "Invalid scrq reset. irq (%d) or msgs(%p).\n",
		scrq->irq, scrq->msgs);
		return -EINVAL;
}

If the expression is true, scrq must be a null pointer and cannot
dereference.

Fixes: 9281cf2d

 ("ibmvnic: avoid memset null scrq msgs")
Signed-off-by: YANG LI <abaci-bugfix@linux.alibaba.com>
Reported-by: Abaci <abaci@linux.alibaba.com>
Acked-by: Lijun Pan <ljp@linux.ibm.com>
Link: https://lore.kernel.org/r/1609312994-121032-1-git-send-email-abaci-bugfix@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>