moveconfig: Remove remove_defconfig()

This is not necessary if simpler code is used. Use the split function and
drop the unnecessary []

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Suggested-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>