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>
diff --git a/drivers/gpu/drm/radeon/radeon_asic.c b/drivers/gpu/drm/radeon/radeon_asic.c
index 0d7664b..d923e4b 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.c
+++ b/drivers/gpu/drm/radeon/radeon_asic.c
@@ -639,7 +639,7 @@
 	.gpu_is_lockup = &evergreen_gpu_is_lockup,
 	.asic_reset = &evergreen_asic_reset,
 	.vga_set_state = &r600_vga_set_state,
-	.gart_tlb_flush = &r600_pcie_gart_tlb_flush,
+	.gart_tlb_flush = &evergreen_pcie_gart_tlb_flush,
 	.gart_set_page = &rs600_gart_set_page,
 	.ring_test = NULL,
 	.ring_ib_execute = NULL,