x86/acpi/boot: Correct acpi_is_processor_usable() check

The logic in acpi_is_processor_usable() requires the online capable
bit be set for hotpluggable CPUs. The online capable bit has been
introduced in ACPI 6.3.

However, for ACPI revisions < 6.3 which do not support that bit, CPUs
should be reported as usable, not the other way around.

Reverse the check.

[ bp: Rewrite commit message. ]

Fixes: e2869bd7af60 ("x86/acpi/boot: Do not register processors that cannot be onlined for x2APIC")
Suggested-by: Miguel Luis <[e-mail]>
Suggested-by: Boris Ostrovsky <[e-mail]>
Signed-off-by: Eric DeVolder <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Tested-by: David R <[e-mail]>
Cc: <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/kernel/acpi/boot.c

···
 	if (lapic_flags & ACPI_MADT_ENABLED)
 		return true;
 
-	if (acpi_support_online_capable && (lapic_flags & ACPI_MADT_ONLINE_CAPABLE))
+	if (!acpi_support_online_capable ||
+	    (lapic_flags & ACPI_MADT_ONLINE_CAPABLE))
 		return true;
 
 	return false;