mwifiex: remove redundant local structures

Avoid use of local structure in the function if the structure is
already allocated by the caller and the structure pointer is passed.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>