mwifiex: remove unnecessary variable initialization

Skip initialization of local variables with some default values
if the values are not going to be used further down the code path.

Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>