fix(cpus): workaround for Cortex-A715 erratum 2804830

Cortex-A715 erratum 2804830 applies to r0p0, r1p0, r1p1 and r1p2,
and is fixed in r1p3.

Under some conditions, writes of a 64B-aligned, 64B granule of
memory might cause data corruption without this workaround. See SDEN
for details.

Since this workaround disables write streaming, it is expected to
have a significant performance impact for code that is heavily
reliant on write streaming, such as memcpy or memset.

SDEN: https://developer.arm.com/documentation/SDEN-2148827/latest/

Change-Id: Ia12f6c7de7c92f6ea4aec3057b228b828d48724c
Signed-off-by: John Powell <john.powell@arm.com>
(cherry picked from commit fcf2ab71ac00122bd382973f6e9f08e30b7eca80)
4 files changed