dsp563xx: rudimentary gdb support

dsp563xx: rudimentary gdb support

This patch add rudimentary gdb support. The gdb register list
order is corrected. All registers are now 32bit width. Events are
send to signalize gdb the current target status. Resume and step
function was corrected to consider a modified pc register. Read/write
memory now support L memory type, this means a memory with alternating
y/x memory words. The memspace variable, used by gdb, is now observed
before a default memory access is initiated. Dummy functions for breakpoint
and watchpoint are added.