net/ice: fix possible null pointer dereference

net/ice: fix possible null pointer dereference

Fix the issues reported by Coverity check, "Null-checking
vsi suggests that it may be null, but it has already been
dereferenced on all paths leading to the check."

Coverity issue: 328509, 328519, 328523
Fixes: e0dcf94a0d7f ("net/ice: support VLAN ops")
Fixes: ff963bfa7cb1 ("net/ice: support RSS")
Cc: stable@dpdk.org
Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>
Reviewed-by: Rami Rosen <ramirose@gmail.com>