This erratum can only be worked around on revisions >= r3p0 because the
register that needs to be accessed only exists in those revisions[1].

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0438g/CIHEAAAD.html

Change-Id: I5d773547d7a09b5bd01dabcd19ceeaf53c186faa
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>