of: remove select of non-existant OF_DEVICE config symbol

The OF_OVERLAY option selects OF_DEVICE, but OF_DEVICE was removed in
commit ba166e900b, "of: remove CONFIG_OF_DEVICE". Remove the unnecessary
select.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Reported-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>