mtd: spi-nor: drop jedec_probe /helper/ function

It's a one-liner doing no magic and its name may be confusing because
it does not have to use JEDEC (e.g. when using alternative read_id).

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Huang Shijie <shijie8@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>