MSI: Cleanup existing MSI quirks

Move MSI quirks in CONFIG_PCI_MSI, document why the serverworks quirk
does not simply set PCI_BUS_FLAGS_NO_MSI, and create a generic quirk
for other chipsets where setting PCI_BUS_FLAGS_NO_MSI is fine.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>