drm/amdgpu: add kernel config for gfx-userqueue

This patch:
- adds a kernel config option "CONFIG_DRM_AMDGPU_NAVI3X_USERQ"
- moves the usequeue initialization code for all IPs under
  this flag
- cover the core userqueue functions under this config
- adds stub function for userqueue ioctl.

so that the userqueue works only when the config is enabled.

V9:  Introduce this patch
V10: Call it CONFIG_DRM_AMDGPU_NAVI3X_USERQ instead of
     CONFIG_DRM_AMDGPU_USERQ_GFX (Christian)
V11: Add GFX in the config help description message.
V12: Add depends on BROKEN for this config, remove this when the rest of
the code is available.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Arvind Yadav <arvind.yadav@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_userqueue.c

@@ -39,6 +39,7 @@ amdgpu_userqueue_cleanup(struct amdgpu_userq_mgr *uq_mgr,
 	kfree(queue);
 }
 
+#ifdef CONFIG_DRM_AMDGPU_NAVI3X_USERQ
 static struct amdgpu_usermode_queue *
 amdgpu_userqueue_find(struct amdgpu_userq_mgr *uq_mgr, int qid)
 {
@@ -279,6 +280,13 @@ int amdgpu_userq_ioctl(struct drm_device *dev, void *data,
 
 	return r;
 }
+#else
+int amdgpu_userq_ioctl(struct drm_device *dev, void *data,
+		       struct drm_file *filp)
+{
+	return 0;
+}
+#endif
 
 int amdgpu_userq_mgr_init(struct amdgpu_userq_mgr *userq_mgr, struct amdgpu_device *adev)
 {