target: Fix an issue with rwp/rbp command in smp targets

If wp/bp is missing at address rwp/rbp won't return zero code (on smp).
Now it fixed.

Fixes: 022e4382

 ("target: Change policy of removing watchpoints/breakpoints.")

Change-Id: I3a3c245f7088fc23227b286d2191fc7f3edba702
Signed-off-by: Kirill Radkin <kirill.radkin@syntacore.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7910


Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>