rndis_wlan: cleanup: byteswap data from device instead of RNDIS_* defines

All other values from device provided buffer are byteswapped, so it seems more
logical to do same for these.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>