linux: make if_getnetworknamespace static

Author: rsmarples

src/if-linux.c

@@ -385,7 +385,7 @@ if_linksocket(struct sockaddr_nl *nl, int protocol, int flags)
 	return fd;
 }
 
-char *
+static char *
 if_getnetworknamespace(char *buf, size_t len)
 {
 	struct stat sb_self, sb_netns;

src/if.h

@@ -212,7 +212,6 @@ int if_ignoregroup(int, const char *);
 bool if_ignore(struct dhcpcd_ctx *, const char *);
 int if_vimaster(struct dhcpcd_ctx *ctx, const char *);
 unsigned short if_vlanid(const struct interface *);
-char * if_getnetworknamespace(char *, size_t);
 int if_opensockets(struct dhcpcd_ctx *);
 int if_opensockets_os(struct dhcpcd_ctx *);
 void if_closesockets(struct dhcpcd_ctx *);