rndis_wlan: fix buffer overflow in rndis_query_oid

rndis_query_oid overwrites *len which stores buffer size to return full size
of received command and then uses *len with memcpy to fill buffer with
command.

Ofcourse memcpy should be done before replacing buffer size.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>