HID: logitech-dj: add debug msg when exporting a HID++ report descriptors

When exporting all other types of report descriptors we print a debug
message. Not doing so for HID++ descriptors makes unaware users think
that no HID++ descriptor was exported.

Signed-off-by: Filipe Laíns <lains@archlinux.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>