dsp563xx: Adding breakpoint/watchpoint support.

Added missing breakpoint/watchpoint implementation to dsp563xx target.
Implementation is not yet complete, which means it does not leverage all
available features of the once debug interface.
This does NOT use the openocd breakpoint/watchpoint command because of
the "special" memory address spaces (X/Y/P/L) of the 56k DSP series.

Change-Id: I6840a3ff1e6fdebb38ab7758f164886aff773af6
Signed-off-by: Bernhard Kiesbauer <bernhard@kiesbauer.com>
Reviewed-on: http://openocd.zylin.com/1468
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>