device: add fcntl.h for musl

Musl requires that this header be explicitly included for O_CREAT,
O_CLOEXEC, etc.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

device.c

@@ -38,6 +38,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <fcntl.h>
 
 #include "cdba-server.h"
 #include "device.h"