video: tegra: host: Use correct dev in ctx alloc

video: tegra: host: Use correct dev in ctx alloc

Recently merged patch for channel specific vm contexts caused a
regression to map-at-submit policy. This patch fixes a NULL pointer
exception caused by the change.

Bug 200041935

Change-Id: Id82730ff8cb90ccd90b29c00d5cd462d02fd153c
Signed-off-by: Arto Merilainen <amerilainen@nvidia.com>
Reviewed-on: http://git-master/r/603848
Reviewed-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Shridhar Rasal <srasal@nvidia.com>