Fix build with clang 16
Bug: https://bugs.gentoo.org/887113
--- a/atmel_fwl.c
+++ b/atmel_fwl.c
@@ -37,7 +37,7 @@ struct atmel_priv_ioctl {
 	unsigned short len;    
 };
 
-main(int argc, char **argv)
+int main(int argc, char **argv)
 {
 	int i, magic, rc, sock = -1;
 	struct ifreq ifr;