mwifiex: Fix invalid port issue

We have to use start port, for TX/RX of single packet,
instead of current aggregating port. This will fix SDIO
CMD53(TX/RX) returning -ETIMEDOUT and halting the data path.

Fixes: 0cb52aac ("mwifiex: do not set multiport flag for tx/rx single packet")
Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>