ev_cdev_write_pending flag is preventing a TX message post for
AT port while MBIM transfer is ongoing.

Removed the unnecessary check around control port TX transfer.
Signed-off-by: NM Chetan Kumar <m.chetan.kumar@linux.intel.com>
Reviewed-by: NSergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>