arm64: ssbd: Restore mitigation status on CPU resume

On a system where firmware can dynamically change the state of the
mitigation, the CPU will always come up with the mitigation enabled,
including when coming back from suspend.

If the user has requested "no mitigation" via a command line option,
let's enforce it by calling into the firmware again to disable it.

Similarily, for a resume from hibernate, the mitigation could have
been disabled by the boot kernel. Let's ensure that it is set
back on in that case.

Change-Id: I02111bcf8f44e0234f50927f078eae454d31e0b6
Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 647d0519b53f440a55df163de21c52a8205431cc
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[isaacm@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>