mpc52xx, digsy_mtc_rev5: Fix Linux crash, if no Flash in bank 2

If no Flash is connected to cs1, Linux crashes, because
reg entries are not correct adapted.

Following fix is needed:
- swap base addresses in CONFIG_SYS_FLASH_BANKS_LIST, as
  flash bank 1 is on chipselect 0 and flash bank 2 on
  chipselect 1
- call fdt_fixup_nor_flash_size() from ft_board_setup()

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <hs@denx.de>
cc: Werner Pfister <Pfister_Werner@intercontrol.de>
cc: Detlev Zundel <dzu@denx.de>