drm/i915/selftests: make mock_drm.h self-contained

Needs i915_drv.h because i915 gets dereferenced.

Cc: Chris Wilson <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/selftests/mock_drm.h

···
 
 #include <drm/drm_file.h>
 
-struct drm_i915_private;
+#include "i915_drv.h"
+
 struct drm_file;
 struct file;