Revert workaround for A77 erratum 1800714

This errata workaround did not work as intended and was revised in
subsequent SDEN releases so we are reverting this change.

This is the patch being reverted:
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/4686



Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I8554c75d7217331c7effd781b5f7f49b781bbebe