staging: ti-st: drop the __KERNEL__

ti_wilink_st.h had the line discipline number which the user-space
daemon refers to, to install and un-install the line discipline upon
request from the shared transport driver via rfkill device.

On moving this line discipline number to standard location of tty.h
drop the __KERNEL__ flag in the header, since the header file would
no longer be used by user-space.

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>