PCI quirks: disable msi on AMD rs4xx internal gfx bridges

Doesn't work reliably for internal gfx.  Fixes kernel bug
https://bugzilla.kernel.org/show_bug.cgi?id=15626

.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: Stable <stable@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>