mwifiex: add sdio multiport aggregation debug information

This patch sdio multi port aggregation statistics which can be
used for debugging. This debug data is collected in
/sys/kernel/debug/mwifiex/mlan0/debug.

Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>