[U-Boot] AT91 Rework

[Jens Scharsig <js_at_ng@scharsoft.de>]

Dear Wolfgang Denk,

We discussed the AT91 defs replaced by C structures.
I have checked the AT91 and the AT91RM9200 tree.
I have planned the following procedure:

1. Add the CONFIG_AT_LEGACY to all affected boards
   (until the board is updated)	
2. Put an warinig to all files that use old defs
3. enclose the old def's with #ifdef CONFIG_AT_LEGACY
4. Add new C stuctures to header files
5. update affected common and driver files
6. next steps t.b.d

An additional aim of the revision should be the union
of the AT91 and AT91RM9200 tree. Some part like UART,
SPI; PIO and so one are the same. Only a lot of devices
like MAC are different.
But I can't see, when this work will be done.

Please tell me, where you think it makes sense to
provide an patch

Best regards

Jens Scharsig