mwifiex: fix command timeout for PCIe chipsets

When WLAN interface is up and running, driver unload and
load was causing command timeout error.

We enable Rx data by updating RX ring read pointer in
init_fw_port(). It should be done when FW is completely
intialialised. Command timeout is fixed in this patch by
moving init_fw_port() call to mwifiex_init_fw_complete().

Signed-off-by: Zhaoyang Liu <liuzy@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>