drm/i915/icl: Find DSI presence for ICL

This patch detects DSI presence for ICL platform
by reading VBT. DSI detection is done while initializing
DSI using newly added function intel_gen11_dsi_init.

v2 by Jani:
 - Preserve old behavour of intel_bios_is_dsi_present()
 - s/intel_gen11_dsi_init/icl_dsi_init/g

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/2324cdfc8918bda3165354e5e0d15053b1074f14.1540900289.git.jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3ea715f..af042b3 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14128,6 +14128,7 @@ static void intel_setup_outputs(struct drm_i915_private *dev_priv)
 		intel_ddi_init(dev_priv, PORT_D);
 		intel_ddi_init(dev_priv, PORT_E);
 		intel_ddi_init(dev_priv, PORT_F);
+		icl_dsi_init(dev_priv);
 	} else if (IS_GEN9_LP(dev_priv)) {
 		/*
 		 * FIXME: Broxton doesn't support port detection via the