staging: vt6656: replace GFP_ATOMIC with GFP_KERNEL for urb allocation

Replace GFP_ATOMIC with GFP_KERNEL during urb buffer allocation.
This makes vnt_alloc_bufs() consistent in setting GFP_KERNEL during
kmalloc() and usb_alloc_urb(). GFP_KERNEL is safe because we are in
process context, not in an interrupt handler, nor holding any spinlock.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>