drm/fbdev: Select fbdev I/O helpers from modules that require them

Fbdev emulation for SHMEM and TTM requires helpers from the fbdev
subsystem. Select them from the modules that use them instead of the
core DRM module.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241014085740.582287-5-tzimmermann@suse.de

drivers/gpu/drm/Kconfig

@@ -11,7 +11,6 @@ menuconfig DRM
 	select DRM_PANEL_ORIENTATION_QUIRKS
 	select DRM_KMS_HELPER if DRM_FBDEV_EMULATION
 	select FB_CORE if DRM_FBDEV_EMULATION
-	select FB_SYSMEM_HELPERS_DEFERRED if DRM_FBDEV_EMULATION
 	select HDMI
 	select I2C
 	select DMA_SHARED_BUFFER
@@ -333,6 +332,7 @@ config DRM_TTM_HELPER
 	tristate
 	depends on DRM
 	select DRM_TTM
+	select FB_SYSMEM_HELPERS_DEFERRED if DRM_FBDEV_EMULATION
 	help
 	  Helpers for ttm-based gem objects
 
@@ -346,6 +346,7 @@ config DRM_GEM_DMA_HELPER
 config DRM_GEM_SHMEM_HELPER
 	tristate
 	depends on DRM && MMU
+	select FB_SYSMEM_HELPERS_DEFERRED if DRM_FBDEV_EMULATION
 	help
 	  Choose this if you need the GEM shmem helper functions