[PATCH] drm/amdgpu: fix building without CONFIG_HMM_MIRROR

[Arnd Bergmann <arnd@arndb.de>]

'struct hmm_mirror' is not defined without the Kconfig option set,
so we cannot include it within another struct:

In file included from drivers/gpu/drm/amd/amdgpu/../amdgpu/amdgpu.h:72:
drivers/gpu/drm/amd/amdgpu/../amdgpu/amdgpu_mn.h:69:20: error: field has incomplete type 'struct hmm_mirror'
        struct hmm_mirror       mirror;
                                ^
drivers/gpu/drm/amd/amdgpu/../amdgpu/amdgpu_mn.h:69:9: note: forward declaration of 'struct hmm_mirror'
        struct hmm_mirror       mirror;

Add the #ifdef around it that is also used for all functions operating
on it.

Fixes: 7590f6d211ec ("drm/amdgpu: Prepare for hmm_range_register API change")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
index 281fd9fef662..b8ed68943625 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h
@@ -65,8 +65,10 @@ struct amdgpu_mn {
 	struct rw_semaphore	lock;
 	struct rb_root_cached	objects;
 
+#ifdef CONFIG_HMM_MIRROR
 	/* HMM mirror */
 	struct hmm_mirror	mirror;
+#endif
 };
 
 #if defined(CONFIG_HMM_MIRROR)
-- 
2.20.0