The workaround for PL310 erratum #753970 can lead to deadlock on systems
with an L220 cache controller.

This patch makes the workaround effective only when the cache controller
is identified as a PL310 at probe time.

Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>