I looked at the userspace code which uses the LPIOC_GET_DEVICE_ID ioctl
and I almost went blind. Let's export it in sysfs instead, and just as a
string instead of with a big-endian length at the beginning of it.

This also prints the message about finding the printer _after_ we know
the minor device number it's going to have, rather than reporting all
printers as 'usblp0'.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>