drm/i915: Fix I915_EXEC_RING_MASK

This was supposed to be a mask of all known rings, but it is being used
by execbuffer to filter out invalid rings, and so is instead mapping high
unused values onto valid rings. Instead of a mask of all known rings,
we need it to be the mask of all possible rings.

Fixes: 549f7365 ("drm/i915: Enable SandyBridge blitter ring")
Fixes: de1add36 ("drm/i915: Decouple execbuf uAPI from internal implementation")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: <stable@vger.kernel.org> # v4.6+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190301140404.26690-21-chris@chris-wilson.co.uk

include/uapi/drm/i915_drm.h

@@ -979,7 +979,7 @@ struct drm_i915_gem_execbuffer2 {
 	 * struct drm_i915_gem_exec_fence *fences.
 	 */
 	__u64 cliprects_ptr;
-#define I915_EXEC_RING_MASK              (7<<0)
+#define I915_EXEC_RING_MASK              (0x3f)
 #define I915_EXEC_DEFAULT                (0<<0)
 #define I915_EXEC_RENDER                 (1<<0)
 #define I915_EXEC_BSD                    (2<<0)