drm/i915: make more headers self-contained

The headers in the gem/selftests/, gt/selftests, gvt/, selftests/
directories have never been compile-tested, but it would be possible
to make them self-contained.

This commit only addresses missing <linux/types.h> and forward
struct declarations.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191108094142.25942-1-yamada.masahiro@socionext.com

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

@@ -33,6 +33,10 @@
 #ifndef _GVT_HYPERCALL_H_
 #define _GVT_HYPERCALL_H_
 
+#include <linux/types.h>
+
+struct device;
+
 enum hypervisor_type {
 	INTEL_GVT_HYPERVISOR_XEN = 0,
 	INTEL_GVT_HYPERVISOR_KVM,