mtd: nand: atmel: Fix EDO mode check

EDO mode should be used when tRC is less than 30ns, but timings are
expressed in picoseconds in the nand_sdr_timings struct.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: f9ce2edd ("mtd: nand: atmel: Add ->setup_data_interface() hooks")
Reported-by: Alexander Dahl <ada@thorsis.com>
Tested-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>