ARM: at91: sama5d2: Enable the use of Galois Tables from ROM

sama5d2 contains in its ROM memory BCH code tables for NAND Flash ECC
correction. Enable the use of the GF tables defined in ROM. This should
speed up the boot process, as the tables are no longer constructed at
runtime. Tested with sama5d2-ptc-ek.

Reported-by: David Mosberger-Tang <davidm@egauge.net>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>