drm/radeon/kms: fix some GART table entry bugs.

1. rv370 can accept 40-bit addresses - also at 24-bit shift not 4 bits
2. rs480 table can be in 40-bit space. - 4 bit shift for top 8 bits
3. rs480 table entries can be in 40-bit space.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index c550932..1b23106 100644
--- a/drivers/gpu/drm/radeon/r100.c
+++ b/drivers/gpu/drm/radeon/r100.c
@@ -110,7 +110,7 @@
 	if (i < 0 || i > rdev->gart.num_gpu_pages) {
 		return -EINVAL;
 	}
-	rdev->gart.table.ram.ptr[i] = cpu_to_le32((uint32_t)addr);
+	rdev->gart.table.ram.ptr[i] = cpu_to_le32(lower_32_bits(addr));
 	return 0;
 }