juno/pvt: Trust the HAL in mod_sensor_driver_api

This driver implements an API defined by the HAL, so
we can be sure that the parameters passed to us do
not need to be sanitized.

Change-Id: I88e09d041f7348c4a22d1e876ed8256faef228c6
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>