drm/i915: introduce for_each_encoder_on_crtc

We already have this pattern at quite a few places, and moving part of
the modeset helper stuff into the driver will add more.

v2: Don't clobber the crtc struct name with the macro parameter ...

v3: Convert two more places noticed by Paulo Zanoni.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@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 6c3a0bb..476c64c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -79,6 +79,10 @@
 
 #define for_each_pipe(p) for ((p) = 0; (p) < dev_priv->num_pipe; (p)++)
 
+#define for_each_encoder_on_crtc(dev, __crtc, intel_encoder) \
+	list_for_each_entry((intel_encoder), &(dev)->mode_config.encoder_list, base.head) \
+		if ((intel_encoder)->base.crtc == (__crtc))
+
 struct intel_pch_pll {
 	int refcount; /* count of number of CRTCs sharing this PLL */
 	int active; /* count of number of active CRTCs (i.e. DPMS on) */