drm/i915: Add TIMESTAMP to register whitelist

This is needed for the Mesa Vulkan driver on Haswell.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Kristian Høgsberg <krh@bitplanet.net>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1457335830-30923-2-git-send-email-jordan.l.justen@intel.com

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -444,6 +444,7 @@ static const struct drm_i915_reg_descriptor gen7_render_regs[] = {
 	REG64(CL_PRIMITIVES_COUNT),
 	REG64(PS_INVOCATION_COUNT),
 	REG64(PS_DEPTH_COUNT),
+	REG64_IDX(RING_TIMESTAMP, RENDER_RING_BASE),
 	REG32(OACONTROL), /* Only allowed for LRI and SRM. See below. */
 	REG64(MI_PREDICATE_SRC0),
 	REG64(MI_PREDICATE_SRC1),