target/hexagon: reduce scope of def_regnum, remove dead assignment

This is intended to address a coverity finding: CID 1527408.

Signed-off-by: Brian Cain <bcain@quicinc.com>
Reviewed-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Message-Id: <20240114234453.4114587-1-bcain@quicinc.com>

target/hexagon/mmvec/decode_ext_mmvec.c

@@ -33,7 +33,6 @@ check_new_value(Packet *pkt)
     const char *dststr = NULL;
     uint16_t def_opcode;
     char letter;
-    int def_regnum;
 
     for (i = 1; i < pkt->num_insns; i++) {
         uint16_t use_opcode = pkt->insn[i].opcode;
@@ -78,15 +77,14 @@ check_new_value(Packet *pkt)
                 }
             }
             if ((dststr == NULL)  && GET_ATTRIB(def_opcode, A_CVI_GATHER)) {
-                def_regnum = 0;
                 pkt->insn[i].regno[use_regidx] = def_oreg;
                 pkt->insn[i].new_value_producer_slot = pkt->insn[def_idx].slot;
             } else {
                 if (dststr == NULL) {
                     /* still not there, we have a bad packet */
                     g_assert_not_reached();
                 }
-                def_regnum = pkt->insn[def_idx].regno[dststr - reginfo];
+                int def_regnum = pkt->insn[def_idx].regno[dststr - reginfo];
                 /* Now patch up the consumer with the register number */
                 pkt->insn[i].regno[use_regidx] = def_regnum ^ def_oreg;
                 /* special case for (Vx,Vy) */