drm/i915/cnl: Fix LSPCON support.

When LSPCON support was extended to CNL
one part was missed on lspcon_init.

So, instead of adding check per platform on lspcon_init
let's use HAS_LSPCON that is already there for that
purpose.

Fixes: ff15947e0f02 ("drm/i915/cnl: LSPCON support is gen9+")
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170816030403.11368-1-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_lspcon.c

@@ -210,8 +210,8 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
 	struct drm_device *dev = intel_dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
-	if (!IS_GEN9(dev_priv)) {
-		DRM_ERROR("LSPCON is supported on GEN9 only\n");
+	if (!HAS_LSPCON(dev_priv)) {
+		DRM_ERROR("LSPCON is not supported on this platform\n");
 		return false;
 	}