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_fbdev_shmem.o: in function `drm_fbdev_shmem_driver_fbdev_probe':
drm_fbdev_shmem.c:(.text+0x1fc): undefined reference to `fb_deferred_io_init'
x86_64-linux-ld: drivers/gpu/drm/drm_fbdev_shmem.o: in function `drm_fbdev_shmem_fb_destroy':
drm_fbdev_shmem.c:(.text+0x2e1): undefined reference to `fb_deferred_io_cleanup'

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

v3:
- Remove FB_CORE from DRM_KMS_HELPER to avoid circular dependency

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

Author: arndb

drivers/gpu/drm/Kconfig

@@ -372,6 +372,7 @@ config DRM_GEM_DMA_HELPER
 config DRM_GEM_SHMEM_HELPER
 	tristate
 	depends on DRM && MMU
+	select FB_CORE if DRM_FBDEV_EMULATION
 	select FB_SYSMEM_HELPERS_DEFERRED if DRM_FBDEV_EMULATION
 	help
 	  Choose this if you need the GEM shmem helper functions