SPM: Add shim layer to Ivy partition and enable PIE

Add a shim layer that runs at S-EL1 to the Ivy partition.
Also enable Ivy to be built with PIE.

Signed-off-by: Ruari Phipps <ruari.phipps@arm.com>
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
Change-Id: I821a8ac99d07200aec93ca29d182f8ab6716616c
9 files changed