ACPI/PCI: PCI MSI _OSC support capabilities called when root bridge added

The _OSC capability OSC_MSI_SUPPORT is set when the root bridge is added
with pci_acpi_osc_support(), so we no longer need to do it in the PCI
MSI driver.  Also adds the function pci_msi_enabled, which returns true
if pci=nomsi is not on the kernel command-line.

Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.c

@@ -2105,8 +2105,6 @@ static int __devinit pci_init(void)
 		pci_fixup_device(pci_fixup_final, dev);
 	}
 
-	msi_init();
-
 	return 0;
 }