coldfire: eb_cpu5282: fix: boot from internal flash

* By a sequence of unfavorable conditions in the config header file, the eb_cpu5282
  booting from  internal stopped after relocation. Blame it is a faulty value of
  CONFIG_SYS_MONITOR_BASE. This patch fix this by replace the wrong condition in
  config header with option in board.cfg

Signed-off-by: Jens Scharsig (BuS Elektronik) <esw@bus-elektronik.de>