drm/i915: make intel_bios.h self-contained

Just a types include required.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/15b8dea022bd80198f91c59f8ad793ebd8fc04f0.1556540889.git.jani.nikula@intel.com

drivers/gpu/drm/i915/Makefile.header-test

@@ -14,6 +14,7 @@ header_test := \
 	i915_timeline_types.h \
 	intel_atomic_plane.h \
 	intel_audio.h \
+	intel_bios.h \
 	intel_cdclk.h \
 	intel_color.h \
 	intel_connector.h \

drivers/gpu/drm/i915/intel_bios.h

@@ -30,6 +30,8 @@
 #ifndef _INTEL_BIOS_H_
 #define _INTEL_BIOS_H_
 
+#include <linux/types.h>
+
 enum intel_backlight_type {
 	INTEL_BACKLIGHT_PMIC,
 	INTEL_BACKLIGHT_LPSS,