Staging: ti-st: cleanup sysfs code

Remove the older way of communicating with user-space
daemon UIM.
The older way involved creating of a new kobj and pid
sysfs file under it, and sending signal using that pid.

Now we communicate via rfkill to user-space UIM.

Background: UIM is the user-space daemon which upon
notification from ldisc driver, opens the tty, sets
default baud and then installs (tiocsetd) the ldisc.

Signed-off-by: Naveen Jain <naveen_jain@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>