Fix minor board specification details.

	* dejagnu/baseboards/atmega128-sim.exp: Minor layout tidy up.
	* dejagnu/baseboards/atmega1280-sim.exp: Correct target -mmcu and
	minor layout tidy-up.
	* dejagnu/baseboards/atxmega128a3-sim.exp: Mionor layout tidy up.

Conflicts (resolved):
	ChangeLog