arm, da85x: update for the ipam390 board

- switch to correct ecc layout used by the RBL
  enable CONFIG_NAND_6BYTES_OOB_FREE_10BYTES_ECC
- update default environment
- change A2CR to correct value for UART boot mode
- adapt cs3cfg timings for nand
- change LED bootmode signalization

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>