drivers:misc:ti-st: remove rfkill dependency

rfkill is no longer used by Texas Instruments shared transport driver to
communicate with user-space.
This patch removes the dependency of rfkill to be enabled to build
shared transport driver in the Kconfig.

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