fix(security): add CVE-2024-7881 mitigation to Cortex-X4

This patch mitigates CVE-2024-7881 [1] by setting CPUACTLR6_EL1[41] to 1
for Cortex-X4 CPU.

[1]: https://developer.arm.com/Arm%20Security%20Center/Arm%20CPU%20Vulnerability%20CVE-2024-7881

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I0bec96d4f71a08a89c6612e272ecfb173f80da20
(cherry picked from commit 6ce6acac911f11979a6cd2ee9cc9041f189c6ec7)
2 files changed