USB: usblcd, fix memory leak

Stanse found a memory leak in lcd_probe. Instead of returning without
releasing the memory, jump to the error label which frees it.

http://stanse.fi.muni.cz/

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>