On the r2p0, r2p1 and r2p2 versions of the Cortex-A9, data corruption
can occur under very rare conditions due to a store buffer optimisation.

This workaround sets a bit in the diagnostic register of the Cortex-A9,
disabling the optimisation and preventing the problem from occurring.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>