staging: synaptics: Update with the kernel object name of touch device

Update with the kernel object name of touch device for getting
the regulator of the synaptics rmi4 touch device.

Signed-off-by: Naveen Kumar Gaddipati <naveen.gaddipati@stericsson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>