sysfb: Make config option dependencies explicit

efifb and vesafb requires sysfb implicitly but this is not stated in
Kconfig. Add the dependency.

With that all drivers that require sysfb depend on it so it can default
to disabled.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/a0fa41e9186653e4c41ad0a28259e5cdc71b1f66.1645822213.git.msuchanek@suse.de