RDMA/siw: Fix tx thread initialization.

Immediately removing the siw module after insertion may
crash in siw_stop_tx_thread(), if the according thread did
not yet had a chance to initialize its wait queue and
siw_stop_tx_thread() tries to wakeup that thread. Initializing
the threads state before spwaning it fixes it.

Reported-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Link: https://lore.kernel.org/r/20230728114418.124328-1-bmt@zurich.ibm.com


Tested-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Leon Romanovsky <leon@kernel.org>