fix(errata): workaround for Cortex-A510 erratum 2371937

Cortex-A510 erratum 2371937 is a Cat B erratum that applies
to revisions r0p0, r0p1, r0p2, r0p3, r1p0, and r1p1. It is
fixed in r1p2. The workaround is to set the ATOM field of
CPUECTLR_EL1 (bits [40:38]) to 0b010, which will force all
cacheable atomic operations to be executed near.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1873351/latest
https://developer.arm.com/documentation/SDEN1873361/latest



Signed-off-by: Akram Ahmad <Akram.Ahmad@arm.com>
Change-Id: Ia219a609a3397e39631de65831ecff8a3cd1227e