MPTAPLE: generate from devicetree.cb

This patch adds support for autogenerating the MPTABLE from
devicetree.cb. This is done by a write_smp_table() declared
weak in mpspec.c. If the mainboard doesn't provide it's own
function, this generic implementation is called.

Syntax in devicetree.cb:

ioapic_irq <APICID> <INTA|INTB|INTC|INTD> <INTPIN>

The ioapic_irq directive can be used in pci and pci_domain
devices. If there's no directive, the autogen code traverses
the tree back to the pci_domain and stops at the first device
which such a directive, and use that information to generate the
entry according to PCI IRQ routing rules.

Change-Id: I4df5b198e8430f939d477c14c798414e398a2027
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/1138
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/devices/device_util.c

@@ -201,6 +201,10 @@ const char *dev_path(device_t dev)
 			sprintf(buffer, "APIC: %02x",
 				dev->path.apic.apic_id);
 			break;
+		case DEVICE_PATH_IOAPIC:
+			sprintf(buffer, "IOAPIC: %02x",
+				dev->path.ioapic.ioapic_id);
+			break;
 		case DEVICE_PATH_PCI_DOMAIN:
 			sprintf(buffer, "PCI_DOMAIN: %04x",
 				dev->path.pci_domain.domain);