powerpc: add adt7461 thermal monitor support to applicable boards

Add thermal monitor support to following boards:
P1022DS, MPC8536DS, P2041RDB, P3041DS, P4080DS, P5020DS, P5040DS

Signed-off-by: Jia Hongtao <B38951@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>