BugLink: http://bugs.launchpad.net/bugs/1540390

Backport I915_EXEC_BSD_MASK from

commit d9da6aa0
Author: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Date:   Wed Jan 27 13:41:09 2016 +0000

    drm/i915: Fix VCS ring selection after uapi decoupling
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>