mwifiex: add manufacturing mode support

By default normal mode is chosen when driver is loaded. This
patch adds a provision to choose manufacturing mode via module
parameters.

Below command loads driver in manufacturing mode
insmod mwifiex.ko mfg_mode=1.

Tested-by: chunfan chen <jeffc@marvell.com>
Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>