drm/amdgpu/display: fix build when CONFIG_DEBUG_FS is not set

amdgpu_dm_crtc_late_register() is only used when CONFIG_DEBUG_FS
is enabled so make it dependent on that.

Fixes: 4cd79f61 ("drm/amd/display: Move connector debugfs to drm")
Cc: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build
Link: https://lists.freedesktop.org/archives/dri-devel/2022-June/359496.htmlSigned-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615210019.28943-1-alexander.deucher@amd.com

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -6617,12 +6617,14 @@ dm_crtc_duplicate_state(struct drm_crtc *crtc)
 	return &state->base;
 }
 
+#ifdef CONFIG_DEBUG_FS
 static int amdgpu_dm_crtc_late_register(struct drm_crtc *crtc)
 {
 	crtc_debugfs_init(crtc);
 
 	return 0;
 }
+#endif
 
 static inline int dm_set_vupdate_irq(struct drm_crtc *crtc, bool enable)
 {
@@ -6720,7 +6722,9 @@ static const struct drm_crtc_funcs amdgpu_dm_crtc_funcs = {
 	.enable_vblank = dm_enable_vblank,
 	.disable_vblank = dm_disable_vblank,
 	.get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
+#if defined(CONFIG_DEBUG_FS)
 	.late_register = amdgpu_dm_crtc_late_register,
+#endif
 };
 
 static enum drm_connector_status