Configuration changes for ADS5121 Rev 3

ADS5121 Rev 3 board is now the default config

config targets are now

ads5121_config
    Rev 3 board with
	PCI
	M41T62 on board RTC
	512MB DRAM

ads5121_rev2_config
    Rev 2 board with
	No PCI
	256MB DRAM

Signed-off-by: Martha Marx <mmarx@silicontkx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: John Rigby <jrigby@freescale.com>