mwifiex: Add missing endian conversion.

Both type and pkt_len variables are in host endian and these should be in
Little Endian in the payload.

Signed-off-by: Tomasz Moń <desowin@gmail.com>
Acked-by: Bing Zhao <bzhao@marvell.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>