lldp: move public macros to sd-lldp.h and namespace them

lldp.h contains definitions of LLDP types, subtypes and capabilities which
should be exposed in public headers. Get rid of the file and move those
definitions to sd-lldp.h with the SD_ prefix.

src/network/networkctl.c

@@ -33,7 +33,6 @@
 #include "ether-addr-util.h"
 #include "fd-util.h"
 #include "hwdb-util.h"
-#include "lldp.h"
 #include "local-addresses.h"
 #include "locale-util.h"
 #include "netlink-util.h"