otrx: include byteswap.h to fix compilation with musl

Fixes #19470

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 45430

package/utils/otrx/src/otrx.c

@@ -9,6 +9,7 @@
  * any later version.
  */
 
+#include <byteswap.h>
 #include <errno.h>
 #include <stdint.h>
 #include <stdio.h>