ti-st: Fix check for pdata->chip_awake function pointer

ll_device_want_to_wakeup(): Fix the NULL pointer check on pdata->chip_awake,
which is performed on the wrong function pointer

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>