package/dialog: fix upstream source URL

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/dialog/dialog.mk

@@ -6,7 +6,7 @@
 
 DIALOG_VERSION = 1.3-20170509
 DIALOG_SOURCE = dialog-$(DIALOG_VERSION).tgz
-DIALOG_SITE = ftp://invisible-island.net/dialog
+DIALOG_SITE = ftp://ftp.invisible-island.net/dialog
 DIALOG_CONF_OPTS = --with-ncurses --with-curses-dir=$(STAGING_DIR)/usr \
 	--disable-rpath-hack
 DIALOG_DEPENDENCIES = host-pkgconf ncurses