Platform/ARM/Morello: Correct the private resources in PPTT

As per ACPI specification, only the head of the list needs to be
listed as a resources by a processor node, as cache node itself
contains a link to the next level of cache.

Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
Reviewed-by: Chris Jones <christopher.jones@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>