refactor(cpus): convert the Cortex-A57 to use cpu helpers

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I1cc10fa91cb9c837386144249dafeb6178d5866e
(cherry picked from commit dbab05efcc33f1da176e10df611a47edc9174612)
1 file changed