dmxVDLRead: if we opened a file, close it instead of leaking it

Reported with other leaks found by cppcheck in bugzilla #50281
https://bugs.freedesktop.org/show_bug.cgi?id=50281

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Keith Packard <keithp@keithp.com>

hw/dmx/config/dmxcompat.c

@@ -228,5 +228,9 @@ dmxVDLRead(const char *filename)
             break;
         }
     }
+
+    if (str != stdin)
+        fclose(str);
+
     return entry;
 }