env_sf: factor out prepare_flash_device

copy&paste code found in single/double buffered code path

Signed-off-by: Andreas Fenkart <afenkart@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Tested-by: Jagan Teki <jagan@openedev.com>
1 file changed