Support more than just the "Misc Control" part of the northbridges.
Support more flags by turning "gart_supported" into a single bit flag
that is stored in a flags member. Clean up related code by using a set
of functions (amd_nb_num(), amd_nb_has_feature() and node_to_amd_nb())
instead of accessing the NB data structures directly. Reorder the
initialization code and put the GART flush words caching in a separate
function.
Signed-off-by: NHans Rosenfeld <hans.rosenfeld@amd.com>
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>