MPC85xx: TQM8548: add support for the TQM8548_BE module

The TQM8548_BE is a variant of the TQM8548 module with NAND and CAN
interface. With NAND support, the image is significantly larger and
TEXT_BASE is adjusted accordingly. U-Boot can be built for this
module with "$ make TQM8548_BE_config".

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>