powerpc/pseries: Add Gen3 definitions for PCIE link speed

Rev3 of the PCI Express Base Specification defines a Supported Link
Speeds Vector where the bit definitions within this field are:

Bit 0 - 2.5 GT/s
Bit 1 - 5.0 GT/s
Bit 2 - 8.0 GT/s

This vector definition is used by the platform firmware to export the
maximum and current link speeds of the PCI bus via the
"ibm,pcie-link-speed-stats" device-tree property.

This patch updates pseries_root_bridge_prepare() to detect Gen3
speed buses (defined by 0x04).
Signed-off-by: NKleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/pci.c

@@ -144,6 +144,9 @@ int pseries_root_bridge_prepare(struct pci_host_bridge *bridge)
 	case 0x02:
 		bus->max_bus_speed = PCIE_SPEED_5_0GT;
 		break;
+	case 0x04:
+		bus->max_bus_speed = PCIE_SPEED_8_0GT;
+		break;
 	default:
 		bus->max_bus_speed = PCI_SPEED_UNKNOWN;
 		break;
@@ -156,6 +159,9 @@ int pseries_root_bridge_prepare(struct pci_host_bridge *bridge)
 	case 0x02:
 		bus->cur_bus_speed = PCIE_SPEED_5_0GT;
 		break;
+	case 0x04:
+		bus->cur_bus_speed = PCIE_SPEED_8_0GT;
+		break;
 	default:
 		bus->cur_bus_speed = PCI_SPEED_UNKNOWN;
 		break;