Rate-limit usblp printer error status messages.

I unplugged my USB printer and almost instantly got several hundred
of these in my kernel message log:
drivers/usb/class/usblp.c: usblp0: error -19 reading printer status
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>