device-port: Change the latency offset type to a signed int.

The latency offset type should be signed (int64_t) so we can also add
a negative latency offset.

This also includes changing the type of the sink/source
offsets and updating pacmd so it handles negative numbers.

src/pulsecore/cli-command.c

@@ -1766,7 +1766,7 @@ static int pa_cli_command_port_offset(pa_core *c, pa_tokenizer *t, pa_strbuf *bu
         return -1;
     }
 
-    pa_device_port_set_latency_offset(port, (pa_usec_t) offset);
+    pa_device_port_set_latency_offset(port, offset);
 
     return 0;
 }