HAL: Replace the 'idx' input param with 'privileged'

In tfm_spm_hal_configure_default_isolation(), a partition index
is passed in to query the partition privilege. Change to pass
in privilege directly instead of the partition index.

Change-Id: Id046431cc8e224a94e83a71564ba2843fabf8ed7
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>