Commit 81737c1d436a (mtd: Fix erasing of devices >4GiB) changed the
prototype of the erase function, but fogot to fix up the stub function
used when no MTD write support is built in.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>