drm/i915: Fix rsvd2 mask when out-fence is returned

GENMASK_ULL wants the high bit of the mask first. The current value
cancels the in-fence when an out-fence is returned.

Fixes: fec0445c ("drm/i915: Support explicit fencing for execbuf")
Testcase: igt/gem_exec_fence/keep-in-fence*
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214191827.8465-1-daniele.ceraolospurio@intel.com
Cc: <stable@vger.kernel.org> # v4.12+

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -2410,7 +2410,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	if (out_fence) {
 		if (err == 0) {
 			fd_install(out_fence_fd, out_fence->file);
-			args->rsvd2 &= GENMASK_ULL(0, 31); /* keep in-fence */
+			args->rsvd2 &= GENMASK_ULL(31, 0); /* keep in-fence */
 			args->rsvd2 |= (u64)out_fence_fd << 32;
 			out_fence_fd = -1;
 		} else {