media: ov5645: Remove unneeded regulator_set_voltage()

There is no need to call regulator_set_voltage() for each regulator
that powers the camera.

The voltage value for each regulator should be retrieved from the
device tree, so remove the unneeded regulator_set_voltage().

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>