drm/i915/skl: Read sink supported rates from edp panel

v2: Using DP_SUPPORTED_LINK_RATES macro for supported_rates array (Satheesh).
v3: Reading dpcd's supported link rates tables based upon edp version in the
same patch.
v4: Move version check under is_edp (Satheesh)
v5: Using le16 for rates, some naming, and removing nested if block (Ville)
v6: Correctly using DP_MAX_SUPPORTED_RATES and removing DP_SUPPORTED_LINK_RATES
(Ville)
v7: Incorrectly removed DP_SUPPORTED_LINK_RATES in v6, re-adding it
v8: Checking return value of intel_dp_dpcd_read_wake() (Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index fbf8149..e05d153 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -626,6 +626,7 @@
 	uint8_t dpcd[DP_RECEIVER_CAP_SIZE];
 	uint8_t psr_dpcd[EDP_PSR_RECEIVER_CAP_SIZE];
 	uint8_t downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
+	__le16 supported_rates[DP_MAX_SUPPORTED_RATES];
 	struct drm_dp_aux aux;
 	uint8_t train_set[4];
 	int panel_power_up_delay;