drm/i915/bxt: edp1.4 Intermediate Freq support

BXT supports following intermediate link rates for edp:
2.16GHz, 2.43GHz, 3.24GHz, 4.32GHz.
Adding support for programming the intermediate rates.

v2: Adding clock in bxt_clk_div struct and then look for the entry with
required rate (Ville)
v3: 'clock' has the selected value, no need to use link_bw or rate_select
for selecting pll(Ville)
v4: Make bxt_dp_clk_val const and remove size (Ville)
v5: Rebased
v6: Removed setting of vco while rebasing in v5, adding it back

Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v4)
Reviewed-by: Vandana Kannan <vandana.kannan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_dp.c

@@ -91,6 +91,8 @@ static const struct dp_link_dpll chv_dpll[] = {
 		{ .p1 = 2, .p2 = 1, .n = 1, .m1 = 2, .m2 = 0x6c00000 } }
 };
 
+static const int bxt_rates[] = { 162000, 216000, 243000, 270000,
+				  324000, 432000, 540000 };
 static const int skl_rates[] = { 162000, 216000, 270000,
 				  324000, 432000, 540000 };
 static const int chv_rates[] = { 162000, 202500, 210000, 216000,
@@ -1170,7 +1172,10 @@ intel_dp_sink_rates(struct intel_dp *intel_dp, const int **sink_rates)
 static int
 intel_dp_source_rates(struct drm_device *dev, const int **source_rates)
 {
-	if (IS_SKYLAKE(dev)) {
+	if (IS_BROXTON(dev)) {
+		*source_rates = bxt_rates;
+		return ARRAY_SIZE(bxt_rates);
+	} else if (IS_SKYLAKE(dev)) {
 		*source_rates = skl_rates;
 		return ARRAY_SIZE(skl_rates);
 	} else if (IS_CHERRYVIEW(dev)) {