msi: introduce ARCH_SUPPORTS_MSI Kconfig option (rev2)

Allows architectures to advertise that they support MSI rather than listing
each architecture as a PCI_MSI dependency.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>