USB: Memory leak in drivers/usb/serial/airprime.c

the commit
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5dda1712


added a memory leak.  In case we cant allocate an urb, we dont free the
buffer and leak it.  Coverity id #1438

Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Acked-by: Andy Gay <andy@andynet.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>