fix(cpus): workaround for Cortex-X3 erratum 2742421

Cortex-X3 erratum 2742421 is a Cat B erratum that applies to
all revisions <= r1p1 and is fixed in r1p2. The workaround is to
set CPUACTLR5_EL1[56:55] to 2'b01.

SDEN documentation:
https://developer.arm.com/documentation/2055130/latest

Signed-off-by: Sona Mathew <sonarebecca.mathew@arm.com>
Change-Id: Idadd323e419739fe909b9b68ea2dbe857846666b
5 files changed