Description: mdesc: fix a missing-check bug in get_vdev_port_node_info()
References:
 https://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc.git/commit/?id=80caf43549e7e41a695c6d1e11066286538b336f
Notes:
 bwh> This is a potential null pointer dereference that looks like it can
 bwh> only be invoked by root or the hypervisor.  Probbaly no security impact.
Bugs:
upstream: released (5.2-rc4) [80caf43549e7e41a695c6d1e11066286538b336f]
4.19-upstream-stable: ignored "Minor issue"
4.9-upstream-stable: ignored "Minor issue"
3.16-upstream-stable: ignored "Minor issue"
sid: released (5.2.6-1)
4.9-stretch-security: N/A "sparc not supported"
3.16-jessie-security: N/A "sparc not supported"