[Blackfin] arch: relocate MAX_SWITCH_{D,I}_CPLBS from the header to the file where it actually gets used.

relocate MAX_SWITCH_{D,I}_CPLBS from the header to the file
where it actually gets used.  this way when we change
CONFIG_MEM_SIZE in our kconfig, we only rebuild one or two files
rather than a whole bunch that implicitly include cplb.h.

this will also remove the ability to clear the swapcount on
the fly, but i really dont think that functionality is important.

ultimate goal is for CONFIG_MEM_SIZE to go away and calculate
this value on the fly based on what u-boot programmed for us.
Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>