soc/intel/common/block/gpio: add code for NMI enabling

Especially server boards, like the Supermicro X11SSM-F, often have a NMI
button and NMI functionality that can be triggered via IPMI. The purpose
of this is to cause the OS to create a system crashdump from a hang
system or for debugging.

Add code for enabling NMI interrupts on GPIOs configured with
PAD_CFG_GPI_NMI. The enabling mechanism is the same as SMI, so the SMI
function was copied and adapted. The `pad_community` struct gained two
variables for the registers.

Also register the NMI for LINT1 in the MADT in accordance to ACPI spec.

Test: Linux detects the NMI correctly in dmesg:
[    0.053734] ACPI: LAPIC_NMI (acpi_id[0xff] high edge lint[0x1])

Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Change-Id: I4fc1a35c99c6a28b20e08a80b97bb4b8624935c9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48090
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/skylake/acpi.c

@@ -522,6 +522,9 @@ unsigned long acpi_madt_irq_overrides(unsigned long current)
 	irqovr = (void *)current;
 	current += acpi_create_madt_irqoverride(irqovr, 0, sci, sci, flags);
 
+	/* NMI */
+	current += acpi_create_madt_lapic_nmi((acpi_madt_lapic_nmi_t *)current, 0xff, 5, 1);
+
 	return current;
 }