Added missing init info field to debian init script. The Short-Description init info field is used by systemd and displayed along with the service name. When it's missing the string 'null' is displayed instead.

#ifndef DROPBEAR_GENSIGNKEY_H
#define DROPBEAR_GENSIGNKEY_H

#include "signkey.h"

int signkey_generate(enum signkey_type type, int bits, const char* filename);

#endif