arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419

arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419

[ Upstream commit b62a42bf467ab8f9b5549cd21b23f1e64ede0bc6 ]

Cores affected by Neoverse-N1 #1542419 could execute a stale instruction
when a branch is updated to point to freshly generated instructions.

To workaround this issue we need user-space to issue unnecessary
icache maintenance that we can trap. Start by hiding CTR_EL0.DIC.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>