drm/i915/gvt: make gvt.h self-contained

Add necessary #includes and forward declarations to make the header
compile on its own.
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/dc4f4d498a39279d12096c1487a3c50d201e5e4f.1607422863.git.jani.nikula@intel.com

drivers/gpu/drm/i915/Makefile

@@ -284,7 +284,6 @@ obj-$(CONFIG_DRM_I915_GVT_KVMGT) += gvt/kvmgt.o
 # exclude some broken headers from the test coverage
 no-header-test := \
 	display/intel_vbt_defs.h \
-	gvt/gvt.h \
 	gvt/mpt.h \
 	gvt/scheduler.h
 

drivers/gpu/drm/i915/gvt/gvt.h

@@ -33,6 +33,10 @@
 #ifndef _GVT_H_
 #define _GVT_H_
 
+#include <uapi/linux/pci_regs.h>
+
+#include "i915_drv.h"
+
 #include "debug.h"
 #include "hypercall.h"
 #include "mmio.h"