drm: Link CMA framebuffer helpers into KMS helper library

Linking the CMA framebuffer helpers into a CMA helper library in
commit 4b2b5e14 ("drm: Move GEM memory managers into modules")
results in linker errors:

  arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: \
	  in function `drm_fb_cma_get_gem_obj': \
	  drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference \
	  to `drm_gem_fb_get_obj'
  arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46: \
	  undefined reference to `drm_gem_fb_get_obj'
  arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46: \
	  undefined reference to `drm_gem_fb_get_obj'
  arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in \
	  function `drm_fb_cma_sync_non_coherent': \
	  drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference \
	  to `drm_atomic_helper_damage_iter_init'
  arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135: \
	  undefined reference to `drm_atomic_helper_damage_iter_next'

Link the CMA framebuffer helpers into the KMS helper library to
fix the problem.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 4b2b5e14 ("drm: Move GEM memory managers into modules")
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20211026175700.27664-1-tzimmermann@suse.de

drivers/gpu/drm/Makefile

@@ -34,7 +34,6 @@ drm-$(CONFIG_DRM_PRIVACY_SCREEN) += drm_privacy_screen.o drm_privacy_screen_x86.
 obj-$(CONFIG_DRM_DP_AUX_BUS) += drm_dp_aux_bus.o
 
 drm_cma_helper-y := drm_gem_cma_helper.o
-drm_cma_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
 obj-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_cma_helper.o
 
 drm_shmem_helper-y := drm_gem_shmem_helper.o
@@ -59,6 +58,7 @@ drm_kms_helper-y := drm_bridge_connector.o drm_crtc_helper.o drm_dp_helper.o \
 
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
+drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
 drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
 drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o