revert(cpus): "Revert workaround for A77 erratum 1800714"

Reinstate the workaround introduced in commit
9bbc03a6e0608a949d66d9da6db12a455b452bfb. The cited change to the SDEN
could not be found and there are no known problems with the workaround.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: Iec9938f173e7565024aca798f224df339de90806
4 files changed