dropbear: fix compile error

Fixes: 0da193ee69 ("dropbear: move failsafe code out of base-files")
Signed-off-by: John Crispin <john@phrozen.org>

package/network/services/dropbear/Makefile

@@ -158,7 +158,8 @@ define Package/dropbear/install
 	$(INSTALL_BIN) ./files/dropbear.init $(1)/etc/init.d/dropbear
 	$(INSTALL_DIR) $(1)/usr/lib/opkg/info
 	$(INSTALL_DIR) $(1)/etc/dropbear
-	$(INSTALL_DIR) ./files/dropbear.failsafe $(1)/lib/preinit/99_10_failsafe_dropbear
+	$(INSTALL_DIR) $(1)/lib/preinit
+	$(INSTALL_DATA) ./files/dropbear.failsafe $(1)/lib/preinit/99_10_failsafe_dropbear
 	$(if $(CONFIG_DROPBEAR_ECC),touch $(1)/etc/dropbear/dropbear_ecdsa_host_key)
 	touch $(1)/etc/dropbear/dropbear_rsa_host_key
 endef