ISO14443: Fix Dead Store (Dead assignement/Dead increment) Warning found by Clang

Change-Id: I63f0b3891030ccc001f81fde94121adad37b555b
Reviewed-on: https://code.wireshark.org/review/12004
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>

epan/dissectors/packet-iso14443.c

@@ -533,7 +533,7 @@ dissect_iso14443_cmd_type_attrib(tvbuff_t *tvb, packet_info *pinfo,
         }
     }
 
-    return tvb_captured_length(tvb);
+    return offset;
 }