include/acpi/acpi.h: Add ACPI_MADT_LAPIC_NMI_ALL_PROCESSORS

This is a magic value that means all processors.
See Table 5-52 Local APIC NMI Structure in ACPI Spec 6.3.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ic2fc060fda21bec44258bcae62ddb230be542759
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50561
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/include/acpi/acpi.h

@@ -514,6 +514,8 @@ typedef struct acpi_madt_lapic_nmi {
 	u8 lint;			/* Local APIC LINT# */
 } __packed acpi_madt_lapic_nmi_t;
 
+#define ACPI_MADT_LAPIC_NMI_ALL_PROCESSORS 0xff
+
 /* MADT: I/O APIC Structure */
 typedef struct acpi_madt_ioapic {
 	u8 type;			/* Type (1) */