As for Spectre variant-2, we rely on SMCCC 1.1 to provide the
discovery mechanism for detecting the SSBD mitigation.
A new capability is also allocated for that purpose, and a
config option.
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>