drm/vmwgfx: Fix regression caused by "drm/ttm: make ttm reservation calls behave like reservation calls"
drm/vmwgfx: Fix regression caused by "drm/ttm: make ttm reservation calls behave like reservation calls"

The call to ttm_eu_backoff_reservation() as part of an error path would cause
a lock imbalance if the reservation ticket was not initialized. This error is
easily triggered from user-space by submitting a bogus command stream.

Signed-off-by: Thomas Hellstrom <a26490dfbee4be3d38287ad6448444504f58193c@vmware.com>
Reviewed-by: Jakob Bornecrantz <6c68cabc7124e43c9b4d50f86510600f69e74c99@vmware.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org
Cc: Maarten Lankhorst <743c2818a341d71b99ed2b566f9f80c2fc288f93@canonical.com>
Cc: Jerome Glisse <0620d428a1bd3756b1319066bf466b3b8be0b2b2@redhat.com>
Cc: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs