drm/i915: default to having backlight if VBT not available

Apparently there are Apple laptops with magic smoke for a VBIOS, which
we fail to find and use. Default to having and setting up backlight in
this case.

This fixes a regression introduced by
commit c675949
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=77831
Reported-and-tested-by: Matteo Cypriani <mcy@lm7.fr>
Cc: stable@vger.kernel.org # 3.15+
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_bios.c

@@ -315,9 +315,6 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 	const struct bdb_lfp_backlight_data *backlight_data;
 	const struct bdb_lfp_backlight_data_entry *entry;
 
-	/* Err to enabling backlight if no backlight block. */
-	dev_priv->vbt.backlight.present = true;
-
 	backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
 	if (!backlight_data)
 		return;
@@ -1088,6 +1085,9 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
 
 	dev_priv->vbt.crt_ddc_pin = GMBUS_PORT_VGADDC;
 
+	/* Default to having backlight */
+	dev_priv->vbt.backlight.present = true;
+
 	/* LFP panel data */
 	dev_priv->vbt.lvds_dither = 1;
 	dev_priv->vbt.lvds_vbt = 0;