drm: rework FB_CORE dependency

The 'select FB_CORE' statement moved from CONFIG_DRM to DRM_CLIENT_LIB,
but there are now configurations that have code calling into fb_core
as built-in even though the client_lib itself is a loadable module:

x86_64-linux-ld: drivers/gpu/drm/drm_fb_helper.o: in function `drm_fb_helper_set_suspend':
drm_fb_helper.c:(.text+0x2c6): undefined reference to `fb_set_suspend'
x86_64-linux-ld: drivers/gpu/drm/drm_fb_helper.o: in function `drm_fb_helper_resume_worker':
drm_fb_helper.c:(.text+0x2e1): undefined reference to `fb_set_suspend'

In addition to DRM_CLIENT_LIB, the 'select' needs to be at least in
DRM_KMS_HELPER and DRM_GEM_SHMEM_HELPER, so add it here.

This patch is the KMS_HELPER part of [1].

Fixes: dadd28d ("drm/client: Add client-lib module")
Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Link: https://patchwork.freedesktop.org/series/141411/ # 1
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Thomas Zimmermann <[email protected]>

Author: arndb

drivers/gpu/drm/Kconfig

@@ -99,6 +99,7 @@ config DRM_KUNIT_TEST
 config DRM_KMS_HELPER
 	tristate
 	depends on DRM
+	select FB_CORE if DRM_FBDEV_EMULATION
 	help
 	  CRTC helpers for KMS drivers.