ARM: at91: atmel_nand: pmecc driver will select the galois table by sector size

Define the galois index table offset in chip head file. So user do not need
to set by himself. Driver will set it correctly according to sector_size.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
ARM: at91: atmel_nand: add code to check the ONFI parameter ECC requirement

1. if CONFIG_SYS_NAND_ONFI_DETECTION is defined, driver will check NAND flash's
   ecc minimum requirement in ONFI parameter.

  a) if CONFIG_PMECC_CAP, CONFIG_PMECC_SECTOR_SIZE are defined. then use it.
     Driver will display a WARNING if the values are different from ONFI
     parameters.

  b) if CONFIG_PMECC_CAP, CONFIG_PMECC_SECTOR_SIZE are not defined, then use
      the value from ONFI parameters.
      * If ONFI ECC parameters are in ONFI extended parameter page, since we
        are not support it, so assume the minimum ecc requirement is 2 bits
        in 512 bytes.
      * For non-ONFI support nand flash, also assume the minimum ecc
        requirement is 2 bits in 512 bytes.

2. if CONFIG_SYS_NAND_ONFI_DETECTION is not defined, just use CONFIG_PMECC_CAP
   and CONFIG_PMECC_SECTOR_SIZE.

Signed-off-by: Josh Wu <josh.wu@atmel.com>