RDMA/irdma: Check vsi pointer before using it

Fix a coverity warning about NULL pointer dereference:
   Dereferencing "vsi", which is known to be "NULL".

Link: https://lore.kernel.org/r/20210708213521.438-1-tatyana.e.nikolova@intel.com


Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1505164 ("Null pointer dereferences")
Fixes: 8498a30e ("RDMA/irdma: Register auxiliary driver and implement private channel OPs")
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Tatyana Nikolova <tatyana.e.nikolova@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>