fix(errata): workaround for Cortex-A510 erratum 2218950

Cortex-A510 erratum 2218950 is a Cat B erratum that applies to revisions
r0p0, r0p1, r0p2, r0p3 and r1p0, and is fixed in r1p1.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN2397239



Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Icb6e369946f8978a08cf8ed5e4452782efb0a77a