drm/i915/dsi: abstract intel_dsi_tlpx_ns()

Will be needed in the future. No functional changes.

Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/2cb427e5bc2ea88e4226bfcf162b3a6f307e32e1.1539613303.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dsi.c

@@ -15,3 +15,16 @@ int intel_dsi_bitrate(const struct intel_dsi *intel_dsi)
 
 	return intel_dsi->pclk * bpp / intel_dsi->lane_count;
 }
+
+int intel_dsi_tlpx_ns(const struct intel_dsi *intel_dsi)
+{
+	switch (intel_dsi->escape_clk_div) {
+	default:
+	case 0:
+		return 50;
+	case 1:
+		return 100;
+	case 2:
+		return 200;
+	}
+}