Description: drm/nouveau: bail out of nouveau_channel_new if channel init fails
References:
 https://bugzilla.redhat.com/show_bug.cgi?id=1876995
 https://lists.freedesktop.org/archives/nouveau/2020-August/036682.html
 https://lore.kernel.org/dri-devel/CACAvsv701GiR6QetL6FGUCQLVn45+1EVGTuA-6Pmw5RtwrvyRQ@mail.gmail.com/
Notes:
 carnil> Commit fixes eeaf06ac1a55 ("drm/nouveau/svm: initial support
 carnil> for shared virtual memory") in 5.1-rc1 so needs check if
 carnil> earlier versions are not affected.
Bugs:
upstream: released (5.12-rc1) [eaba3b28401f50e22d64351caa8afe8d29509f27]
5.10-upstream-stable: released (5.10.20) [e3fcff9f45aa82dacad26e5828598340d2742f47]
4.19-upstream-stable: N/A "Vulnerable code introduced later"
4.9-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.10.19-1) [bugfix/all/drm-nouveau-bail-out-of-nouveau_channel_new-if-chann.patch]
4.19-buster-security: N/A "Vulnerable code introduced later"
4.9-stretch-security: N/A "Vulnerable code introduced later"