usb: isp1362-hcd: Quieten printks

These messages just clutter the log and provide no useful information to
the user, so make them pr_debug().

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>