The errata is enabled by default on r0p4, which is confusing given that
we state we do not enable errata by default.

This patch clarifies this sentence by saying it is enabled in hardware
by default.

Change-Id: I70a062d93e1da2416d5f6d5776a77a659da737aa
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>