mwifiex: stop checking for NULL drvata/intfdata

These are never NULL, so stop making people think they might be.

I don't change this for SDIO because SDIO has a racy card-reset handler
that reallocates this struct. I'd rather not touch that mess right now.

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