drm/i915: add HAS_DP_MST feature test macro

Be in line with other features that we have.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 6a66d6b..11e0059 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2448,6 +2448,9 @@
 
 #define HAS_IPS(dev)		(IS_HSW_ULT(dev) || IS_BROADWELL(dev))
 
+#define HAS_DP_MST(dev)		(IS_HASWELL(dev) || IS_BROADWELL(dev) || \
+				 INTEL_INFO(dev)->gen >= 9)
+
 #define HAS_DDI(dev)		(INTEL_INFO(dev)->has_ddi)
 #define HAS_FPGA_DBG_UNCLAIMED(dev)	(INTEL_INFO(dev)->has_fpga_dbg)
 #define HAS_PSR(dev)		(IS_HASWELL(dev) || IS_BROADWELL(dev) || \