drm/amdgpu: more descriptive message if HMM not enabled

If using old kernel config file, CONFIG_ZONE_DEVICE is not selected,
so CONFIG_HMM and CONFIG_HMM_MIRROR is not enabled, the current driver
error message "Failed to register MMU notifier" is not clear. Inform
user with more descriptive message on how to fix the missing kernel
config option.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109808

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_mn.h

@@ -53,6 +53,8 @@ static inline struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev,
 }
 static inline int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
 {
+	DRM_WARN_ONCE("HMM_MIRROR kernel config option is not enabled, "
+		      "add CONFIG_ZONE_DEVICE=y in config file to fix this\n");
 	return -ENODEV;
 }
 static inline void amdgpu_mn_unregister(struct amdgpu_bo *bo) {}