fix(cpus): workaround for Cortex-A78C erratum 1827440

Cortex-A78C erratum 1827440 is a Cat B erratum that applies to
revision r0p0 and is fixed in r0p1.

The workaround is to set CPUACTLR2_EL1[2], which forces atomic store
operations to write-back memory to be performed in the L1 data cache.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1707916/latest



Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: I41d8ef48f70216ec66bf2b0f4f03ea8d8c261ee7