[POWERPC] Add QE device tree node definition

OF device tree node spec used in QE/8360 support patches.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Jiang Bo <Tanya.jiang@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>