qtnfmac: module param sanity check

Linux built-in circ_buf implementation assumes that that the
circular buffer length is a power of 2. Make sure that
rx and tx descriptor queue lengths are power-of-2.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>