qemu: Fix mis-merge of qemuBuildSerialCommandLine

Commit id '5ab86400' misapplied a merge of commit id '01924475'
to place the "-chardev" command after formatting the character
backend value.

src/qemu/qemu_command.c

@@ -8388,12 +8388,12 @@ qemuBuildSerialCommandLine(virLogManagerPtr logManager,
 
         /* Use -chardev with -device if they are available */
         if (virQEMUCapsSupportsChardev(def, qemuCaps, serial)) {
-            virCommandAddArg(cmd, "-chardev");
             if (!(devstr = qemuBuildChrChardevStr(logManager, cmd, def,
                                                   &serial->source,
                                                   serial->info.alias,
                                                   qemuCaps)))
                 return -1;
+            virCommandAddArg(cmd, "-chardev");
             virCommandAddArg(cmd, devstr);
             VIR_FREE(devstr);