sensor: Reintroduce guarded scmi_senosr header inclusion
Created by: nicola-mazzucato-arm
Previous commit 989816611
removed the scmi_sensor header inclusion,
but that breaks the build when SENSOR_EVENTS are selected.
Reintroduce the header but this time guarded by its build definition.
Change-Id: I1200d78bafa84329a35e61f222cfde45f490053d Signed-off-by: Nicola Mazzucato nicola.mazzucato@arm.com