[POWERPC] prpmc2800: Convert DTS to v1 and add labels

Update the prpmc2800 DTS file to version 1 and add labels.
I verified that there was no change in the resulting dtb file.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>