arm64: alternatives: proton-pack: prepare for cap changes

The spectre patching callbacks use cpus_have_final_cap(), and subsequent
patches will make it invalid to call cpus_have_final_cap() before
alternatives patching has completed.

In preparation for said change, this patch modifies the spectre patching
callbacks use cpus_have_cap(). This is not subject to patching, and will
dynamically check the cpu_hwcaps array, which is functionally equivalent
to the existing behaviour.

There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220912162210.3626215-4-mark.rutland@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/proton-pack.c

@@ -586,7 +586,7 @@ void __init spectre_v4_patch_fw_mitigation_enable(struct alt_instr *alt,
 	if (spectre_v4_mitigations_off())
 		return;
 
-	if (cpus_have_final_cap(ARM64_SSBS))
+	if (cpus_have_cap(ARM64_SSBS))
 		return;
 
 	if (spectre_v4_mitigations_dynamic())