The caller will guarantee that msg won't be null. Remove
the unneeded null pointer check which caused a Coverity
warning.
Coverity issue: 323484
Fixes: 8f972312b8f4 ("vhost: support vhost-user")
Cc: stable@dpdk.org
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>