mtd: nand: increase the max eccpos size to 448

Increase the max eccpos size to support 8k page nand.

Signed-off-by: Raphaël Poggi <poggi.raph@gmail.com>
mtd: atmel_nand: increase chip_delay

Some nand like Micron MT29F32G08ABAAAWP need more than 20us.

Signed-off-by: Raphaël Poggi <poggi.raph@gmail.com>
mtd: atmel_nand: enable PMECC for 8k page nand

Enable the PMECC to support 8k page.

Signed-off-by: Raphaël Poggi <poggi.raph@gmail.com>
mtd: atmel_nand: add has_pmecc member

This commit replace the usage of CONFIG_NAND_ATMEL_PMECC
by a new member called: has_pmecc. This member is directly initialise
in board specific code.

Signed-off-by: Raphaël Poggi <poggi.raph@gmail.com>
arm: board: initialise member has_pmecc

Initialise the member has_pmecc on boards which support it.

Signed-off-by: Raphaël Poggi <poggi.raph@gmail.com>