fix(errata): workaround for Cortex-A78C erratum 2395411

Cortex-A78C erratum 2395411 is a Cat B erratum that affects
revisions r0p1 and r0p2, and is currently open. The workaround
is to set CPUACTLR2_EL1[40] to 1, which will disable folding
of demand requests into older prefetches with L2 miss requests
outstanding.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN2004089/latest



Signed-off-by: Akram Ahmad <Akram.Ahmad@arm.com>
Change-Id: I4f0fb278ac20a2eb4dd7e4efd1b1246dd85e48c4