refactor(cpus): shorten errata flag defines

refactor(cpus): shorten errata flag defines

The cpu-ops makefile has errata flag definition and flag processing done
per flag in separate parts in the file. Rework this to make a list and
do this in a much more concise way.

To ensure no flags were missed, a bash script [1] was used to verify all
errata flags made it across. Only the first few flags with different
naming were checked manually.

[1]:
sed -n "s/CPU_FLAG_LIST += ERRATA_\(.*\)/\1/p" lib/cpus/cpu-ops.mk > \
	/tmp/new
git checkout origin/master
sed -n "s/ERRATA_\([[:alnum:]_-]*\)\s*?=0/\1/p" lib/cpus/cpu-ops.mk > \
	/tmp/old
diff /tmp/old /tmp/new

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I3b88af46838cc26f42d2c66b31f96c0855fa406c