[POWERPC] PowerPC MSI infrastructure

This provides the architecture specific hooks to support MSI on
powerpc.  We implement the newly added arch_setup_msi_irqs() and
arch_teardown_msi_irqs(), and then delegate to ppc_md routines.

Platforms that don't implement MSI will leave the ppc_md calls blank,
arch_msi_check_device() will detect this and return ENOSYS. Drivers
should detect this error and continue to use LSI.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 67668fd..abb13cf 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -682,6 +682,7 @@
 		&& !PPC_85xx && !PPC_86xx
 	default PCI_PERMEDIA if !4xx && !CPM2 && !8xx && APUS
 	default PCI_QSPAN if !4xx && !CPM2 && 8xx
+	select ARCH_SUPPORTS_MSI
 	help
 	  Find out whether your system includes a PCI bus. PCI is the name of
 	  a bus system, i.e. the way the CPU talks to the other stuff inside