mwifiex: fix IBSS data path issue.

The port_open flag is not applicable for IBSS mode. IBSS data
path was broken when port_open flag was introduced.
This patch fixes the problem by correcting the checks.

Fixes: 5c894633

 ("mwifiex: enable traffic only when port is open")
Signed-off-by: chunfan chen <jeffc@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>