scmi_clock: Fix type of clock_id in get_clock_id

The type of the clock_id is does not match its corresponding
id that comes from the payload and nor with the type expected
by the resource permission module.

Change clock_id to uint32_t to match the correct type.

Change-Id: Iad82407be8a74670303919c4f369f839dd9f1019
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>