USB: kobil_sct: fix non-atomic allocation in write path

Write may be called from interrupt context so make sure to use
GFP_ATOMIC for all allocations in write.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>