drm/radeon/kms/evergreen: add gart support

Gart setup is more or less like r7xx.  Copy
rv770d.h to evergreend.h and fix up changes.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
4 files changed