staging/rts_pstor: use kthread_run instead doing kthread_create and wake_up_process

with kthread_create we need to call wake_up_process to run the thread,
this can be done using the macro kthread_run, which creates and if thread
creation is succeeded starts the thread by calling wake_up_process,

and also there are two more threads in the rts_pstor, which calls
kthread_run instead calling kthread_create and another call to the
wake_up_process, so with this change the creation of rtsx_scan_thread
will be in consistency with the other control and poll threads.

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>