drm: NULL pointer dereference [null-pointer-deref] (CWE 476) problem

The Parfait (version 2.1.0) static code analysis tool found the
following NULL pointer derefernce problem.

- drivers/gpu/drm/drm_dp_mst_topology.c
The call to drm_dp_calculate_rad() in function drm_dp_port_setup_pdt()
could result in a NULL pointer being returned to port->mstb due to a
failure to allocate memory for port->mstb.

Change-Id: I52baaba3d2d7faf706a221111b131cc8ca7ec897
Signed-off-by: Joe Moriarty <joe.moriarty@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180212195144.98323-3-joe.moriarty@oracle.com
Git-commit: 22a07038c0eaf4d1315a493ce66dcd255accba19
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Steve Cohen <cohens@codeaurora.org>