UPSTREAM: ARM: report Spectre v2 status through sysfs

commit 9dd78194 upstream.

As per other architectures, add support for reporting the Spectre
vulnerability status via sysfs CPU.

Bug: 215557547
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I426186db1fa21e590de65b70ed531fbf086b176d