mtd: spi-nor: add Spansion S25FS512S ID

Spansion S25FS512S flash is currently misdetected as S25FL512S since the
latter uses 5-byte JEDEC ID, while the 6th ID byte (family ID) is different
on those chips. Add the 6-byte S25FS512S ID before S25FL512S ID in order
not to break the existing S25FS512S users.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>