drm/i915: make i915_pvinfo.h self-contained

Add the minimal includes/declarations to make the header self-contained,
and ensure it stays that way.
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/20190626144020.2155-7-jani.nikula@intel.com

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

@@ -12,6 +12,7 @@ header_test := \
 	i915_irq.h \
 	i915_params.h \
 	i915_priolist_types.h \
+	i915_pvinfo.h \
 	i915_reg.h \
 	i915_scheduler_types.h \
 	i915_utils.h \

drivers/gpu/drm/i915/i915_pvinfo.h

@@ -24,6 +24,8 @@
 #ifndef _I915_PVINFO_H_
 #define _I915_PVINFO_H_
 
+#include <linux/types.h>
+
 /* The MMIO offset of the shared info between guest and host emulator */
 #define VGT_PVINFO_PAGE	0x78000
 #define VGT_PVINFO_SIZE	0x1000