mwifiex: make tx packet 64 byte DMA aligned

This patch adds support for DMA alignment of 64 bytes for TX packets.

Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>