Clear Debug Watchpoint

Clears a debug watchpoint that was previously set using the
Set Debug Watchpoint function (Int 31H Fn 0B00H), and
releases the watchpoint
handle.

Call With:

   AX     = 0B01H
   BX     = watchpoint handle

Returns:

   if function successful
   Carry flag= clear

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8023H   invalid handle