refactor(cpus): convert the Cortex-A53 to use cpu helpers

Also, convert checker functions of errata which are enabled for all cpu
revisions to report correctly in preparation of the errata ABI.

Although the script from commit 250919 was used to check that errata
code did not change, this CPU only loosely adhered to convention and its
output was not particularly useful. Nevertheless, the discrepancies were
manually verified. All errata have been checked that they get invoked.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I988db6e7b6d1732f1d2258dbdf945cb475781894
1 file changed