drm/radeon/kms: vram sizing on certain r100 chips needs workaround.

If an rn50/r100/m6/m7 GPU has < 64MB RAM, i.e. 8/16/32, the
aperture used to calculate the MC_FB_LOCATION needs to be worked
out from the CONFIG_APER_SIZE register, and not the actual vram size.

TTM VRAM size was also being initialised wrong, use actual vram size
to initialise it.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r520.c b/drivers/gpu/drm/radeon/r520.c
index 0a981e2..09fb0b6 100644
--- a/drivers/gpu/drm/radeon/r520.c
+++ b/drivers/gpu/drm/radeon/r520.c
@@ -95,8 +95,8 @@
 		       "programming pipes. Bad things might happen.\n");
 	}
 	/* Write VRAM size in case we are limiting it */
-	WREG32(RADEON_CONFIG_MEMSIZE, rdev->mc.vram_size);
-	tmp = rdev->mc.vram_location + rdev->mc.vram_size - 1;
+	WREG32(RADEON_CONFIG_MEMSIZE, rdev->mc.real_vram_size);
+	tmp = rdev->mc.vram_location + rdev->mc.mc_vram_size - 1;
 	tmp = REG_SET(R520_MC_FB_TOP, tmp >> 16);
 	tmp |= REG_SET(R520_MC_FB_START, rdev->mc.vram_location >> 16);
 	WREG32_MC(R520_MC_FB_LOCATION, tmp);