mwifiex: get rid of mwifiex_do_flr wrapper

This patch gets rid of mwifiex_do_flr. We will call
mwifiex_shutdown_sw() and mwifiex_reinit_sw() directly.
These two general purpose functions will be useful for
sdio card reset handler.

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