board/t2080rdb: some update for t2080rdb

- update readme.
- add CONFIG_SYS_CORTINA_FW_IN_* for loading Cortina PHY CS4315
  ucode from NOR/NAND/SPI/SD/REMOTE.
- update cpld vbank with SW3[5:7]=000 as default vbank0 instead of
  previous SW3[5:7]=111 as default vbank.
- fix CONFIG_SYS_I2C_EEPROM_ADDR_LEN to 2.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
4 files changed