input: synaptics_dsx_2.6: correct secure_touch_init function

In synaptics_dsx_2.6 touch driver, secure_touch_init tries to get
the QUP clocks for the secure touch functionality. But as these
calls are optional and TZ might get the owenership of these clocks,
this change removes the error return statement, so that the
secure touch can be initialized properly.

Change-Id: I12b5075d484cd397bfb423479589e159a2193f31
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>