ARC: Write to _addrWriteBack field in dsmArcOneInst

Field _addrWriteBack was not written to result structure. This field is required by GDB to properly recognize prologue in functions without full debug information.

Signed-off-by: Anton Kolesov <akolesov@synopsys.com>
(cherry picked from commit fae707bd433574a6b47dcffb6cec9c4699f0e5c2)