[PATCH] MPC8xx Idle support for 2.4.28

Hi there

The following patch implements idling support for the 8xx.

The patch works on the DUET family and the Normal Low mode
but could also work on other 8xxs easily; I just don't have
access to any other boards.

It's 2.4 for now since most people with 8xx's are on 2.4 still.

By using it on a 870 I see a power savings of ~400mW on a
133MHz/66MHz.

Regards

Pantelis

P.S. Many thanks to Mr. Conn Clark a.k.a. Obscene_CNN,
for it's only patch on an attempt.

P.S #2. There are alot of errata regarding PLPRCR for 8xx,
on older revisions of 8xx. Make sure you read them...

Signed-off-by: Pantelis Antoniou <redacted>