drm/i915/bxt: Remove the preliminary_hw_support flag

Broxton is now part of CI which doesn't indicate any major problems so
enable the driver by default.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467384045-17028-1-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_pci.c

@@ -331,7 +331,6 @@ static const struct intel_device_info intel_skylake_gt3_info = {
 };
 
 static const struct intel_device_info intel_broxton_info = {
-	.is_preliminary = 1,
 	.is_broxton = 1,
 	.gen = 9,
 	.need_gfx_hws = 1, .has_hotplug = 1,