Blackfin arch: SMP supporting patchset: Blackfin header files and machine common code

Blackfin dual core BF561 processor can support SMP like features.
https://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:smp-like



In this patch, we provide SMP extend to Blackfin header files
and machine common code

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>