mwifiex: use module_*_driver helper macros

After user_rmmod global flag removal, *_init_module() and
*_cleanup_module() have become just a wrapper functions.
We will get rid of them with the help of module_*_driver() macros.

For pcie, existing ".init_if" handler has same name as what
module_pcie_driver() macro will create. Let's rename it to
avoid conflict.

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