V4L/DVB (4990): Cpia2/cpia2_usb.c: fix error-path leak

Free previously allocated memory (in array elements) if kmalloc() returns
NULL in submit_urbs().

Signed-off-by: Amit Choudhary <amit2030@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>