mwifiex: remove explicit mwifiex_complete_cmd calls

standard call chain when releasing a cmd node:
mwifiex_recycle_cmd_node
-> mwifiex_insert_cmd_to_free_q
-> mwifiex_complete_cmd, if wait_q_enabled

calling mwifiex_complete_cmd explicitly and setting
wait_q_enabled = false is redundant

Signed-off-by: Andreas Fenkart <afenkart@gmail.com>
Acked-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>