drm/radeon: upgrade to 1.27 - make PCI GART more flexible

radeon: make PCI GART aperture size variable, but making table size variable
    This is precursor to getting a TTM backend for this stuff, and also
    allows the PCI table to be allocated at fb 0
radeon: add support for reverse engineered xpress200m

    The IGPGART setup code was traced using mmio-trace on fglrx by myself
    and Phillip Ezolt <phillipezolt@gmail.com> on dri-devel.

    This code doesn't let the 3D driver work properly as the card has no
    vertex shader support.

    Thanks to Matthew Garrett + Ubuntu for providing me some hardware to do this
    work on.

Signed-off-by: Dave Airlie <airlied@linux.ie>