feat(spmc): enable the SPMC to pass the linear core ID in a register

Add TF-A implementation defined behaviour to provide the linear core
ID in the x4 register when bringing up an SP.

Signed-off-by: Marc Bonnici <marc.bonnici@arm.com>
Change-Id: I6cb215841097b264d252ec0262b0b7272be99d41
1 file changed