OVERLAY_FS config symbol selects EXPORTFS since 4.12 kernel, we have
OVERLAY_FS enabled by default, so enable EXPORTFS in the generic config
of 4.14 and remove this option from platform specific configs.
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
(cherry picked from commit a08b0d0c3149060f1585ad3ea2ea3edfde71bce4)
1f26cfc92b