drm/i915/vlv: Make the vlv_dpio_read/vlv_dpio_write more PHY centric

vlv_dpio_read/write should be describe more in PHY centric instead of
display controller centric.
Create a enum dpio_channel for channel index and enum dpio_phy for PHY
index.  This should better to gather for upcoming platform.

v2: Rebase the code based on
drm/i915/vlv: Fix typo in the DPIO register define.

v3: Rename vlv_phy to dpio_phy_iosf_port and define additional macro
DPIO_PHY, and remove unrelated change. (Ville)

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Chon Ming Lee <chon.ming.lee@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.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 efca30d..c546316 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -88,6 +88,18 @@
 };
 #define port_name(p) ((p) + 'A')
 
+#define I915_NUM_PHYS_VLV 1
+
+enum dpio_channel {
+	DPIO_CH0,
+	DPIO_CH1
+};
+
+enum dpio_phy {
+	DPIO_PHY0,
+	DPIO_PHY1
+};
+
 enum intel_display_power_domain {
 	POWER_DOMAIN_PIPE_A,
 	POWER_DOMAIN_PIPE_B,
@@ -1403,6 +1415,7 @@
 	int num_shared_dpll;
 	struct intel_shared_dpll shared_dplls[I915_NUM_PLLS];
 	struct intel_ddi_plls ddi_plls;
+	int dpio_phy_iosf_port[I915_NUM_PHYS_VLV];
 
 	/* Reclocking support */
 	bool render_reclock_avail;