Device tree updates

Changes to match 5121 device tree going mainline in 2.6.25.

Change OF_SOC from "soc5121" to plain "soc".
Remove unneeded "ref-frequency" fixups.
Remove "address" enetaddr fixup.

Add bus-frequency fixup for old OF_SOC so old
kernels with old device trees will work with new
u-boot with 66MHz IPS clock

Signed-off-by: John Rigby <jrigby@freescale.com>