drm/radeon: Fix VRAM size calculation for VRAM >= 4GB

Add ULL prefix to avoid overflow.

Signed-off-by: Niels Ole Salscheider <niels_ole@salscheider-online.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 105bafb..06c261b 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -3405,8 +3405,8 @@
 		rdev->mc.real_vram_size = RREG32(CONFIG_MEMSIZE);
 	} else {
 		/* size in MB on evergreen/cayman/tn */
-		rdev->mc.mc_vram_size = RREG32(CONFIG_MEMSIZE) * 1024 * 1024;
-		rdev->mc.real_vram_size = RREG32(CONFIG_MEMSIZE) * 1024 * 1024;
+		rdev->mc.mc_vram_size = RREG32(CONFIG_MEMSIZE) * 1024ULL * 1024ULL;
+		rdev->mc.real_vram_size = RREG32(CONFIG_MEMSIZE) * 1024ULL * 1024ULL;
 	}
 	rdev->mc.visible_vram_size = rdev->mc.aper_size;
 	r700_vram_gtt_location(rdev, &rdev->mc);