drm/i915: add enumeration for DDI ports

There are 5 DDI ports on Haswell. Port A is always enabled, and is the one
connected to eDP, and Port E is the one that can be connected to the PCH
using FDI protocol.  Ports B, C, D and E can be used for digital outputs.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@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 d7a5146..b617cd5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -63,6 +63,16 @@
 };
 #define plane_name(p) ((p) + 'A')
 
+enum port {
+	PORT_A = 0,
+	PORT_B,
+	PORT_C,
+	PORT_D,
+	PORT_E,
+	I915_MAX_PORTS
+};
+#define port_name(p) ((p) + 'A')
+
 #define I915_GEM_GPU_DOMAINS	(~(I915_GEM_DOMAIN_CPU | I915_GEM_DOMAIN_GTT))
 
 #define for_each_pipe(p) for ((p) = 0; (p) < dev_priv->num_pipe; (p)++)