main/open-lldp: fix rebuild error
missing string.h
clif.c: In function 'clif_open':
clif.c:54:9: error: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
54 | memset(clif, 0, sizeof(*clif));
| ^~~~~~
clif.c:40:1: note: include '<string.h>' or provide a declaration of 'memset'
39 | #include "clif_msgs.h"
+++ |+#include <string.h>
40 |
clif.c:54:9: warning: incompatible implicit declaration of built-in function 'memset' [-Wbuiltin-declaration-mismatch]
54 | memset(clif, 0, sizeof(*clif));
| ^~~~~~
clif.c:54:9: note: include '<string.h>' or provide a declaration of 'memset'
clif.c: In function 'clif_attach_helper':
clif.c:187:25: error: implicit declaration of function 'memcmp' [-Wimplicit-function-declaration]
187 | if (len == 4 && memcmp(rbuf, "R00", 3) == 0)