mpc85xx: Update linker scripts for Freescale boards

* Move to using absolute addressing always.  Makes the scripts a bit more
  portable and common
* Moved .bss after the end of the image.  These allows us to have more
  room in the resulting binary image for code and data.
* Removed .text object files that aren't really needed
* Make sure _end is 4-byte aligned as the .bss init code expects this.
  (Its possible that the end of .bss isn't 4-byte aligned)

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>