[Blackfin] arch: remove duplicated prototypes for internal cplb structures...

[Blackfin] arch: remove duplicated prototypes for internal cplb structures from the global blackfin header

remove duplicated prototypes for internal cplb structures from
the global blackfin header as nothing else should be accessing these

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>