mtd: fix endianness detection on musl

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Acked-by: John Crispin <john@phrozen.org>

package/system/mtd/src/mtd.c

@@ -23,6 +23,7 @@
 
 #define _GNU_SOURCE
 #include <byteswap.h>
+#include <endian.h>
 #include <limits.h>
 #include <unistd.h>
 #include <stdlib.h>

package/system/mtd/src/seama.c

@@ -22,6 +22,7 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  */
 
+#include <endian.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>