mwifiex: handle an error path correctly

In failure case locks are not allocated in mwifiex_register().
So mwifiex_free_lock_list() routine call becomes redundant.
Also we don't need to check return type for mwifiex_init_lock_list()
routine. It never fails.

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>