Improve MSI detection v3

[PATCH 0/6] Improve MSI detection v3

Here's another set of patches to cleanup MSI detection.
There's only blacklisting (cleanup for non-PCI-E chipsets and
addition of HT cap checks).

#1 - Merge existing MSI disabling quirks
#2 - Rename PCI_CAP_ID_HT_IRQCONF to PCI_CAP_ID_HT
#3 - Blacklist PCI-E chipsets depending on Hypertransport MSI capabality
#4 - Factorize common MSI detection code from pci_enable_msi() and msix()
#5 - Stop inheriting bus flags and check root chipset bus flags instead
#6 - Drop pci_msi_quirk

Only #3 brings an important feature. The others are mostly cosmetic.
#1 defines a generic quirk to disable MSI. It will probably end up being
used for lots of MSI-broken chipset.

These patches are against 2.6.17-rc6-mm2.

Brice Goglin