mtd: atmel_nand: Disable subpage NAND write when using Atmel PMECC

Crash detected on sam5d35 and its pmecc nand ecc controller.

The problem was a call to chip->ecc.hwctl from nand_write_subpage_hwecc
(nand_base.c) when we write a sub page.
chip->ecc.hwctl function is not set when we are using PMECC controller.
As a workaround, set NAND_NO_SUBPAGE_WRITE for PMECC controller in
order to disable sub page access in nand_write_page.

Signed-off-by: Herve Codina <Herve.CODINA@celad.com>
Acked-by: Josh Wu <josh.wu@atmel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Brian Norris <computersforpeace@gmail.com>