fix(cpus): correct CVE-2024-7881 workaround and drop duplicate erratum

Fix the CVE-2024-7881 [1] workaround for C1-Pro. The previously
implemented erratum 3684268 [2] programmed the same control bit and
overlapped functionally with the CVE workaround, so the duplicate
erratum is removed.

Reference:
[1] https://developer.arm.com/documentation/110326/latest/
[2] https://developer.arm.com/documentation/SDEN-3273080/latest/

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I6207c49486e4020f34c862ad40ec3137bd3684cc