ice: always check VF VSI pointer values

In the Linux kernel, the following vulnerability has been resolved: ice: always check VF VSI pointer values The ice_get_vf_vsi function can return NULL in some cases, such as if handling messages during a reset where the VSI is being removed and recreated. Several places throughout the driver do not bother to check whether this VSI pointer is valid. Static analysis tools maybe report issues because they detect paths where a potentially NULL pointer could be dereferenced. Fix this by checking the return value of ice_get_vf_vsi everywhere.