drm/msm: fix LLC not being enabled for mmu500 targets

mmu500 targets don't have a "cx_mem" region, set llc_mmio to NULL in that
case to avoid the IS_ERR() condition in a6xx_llc_activate().

Fixes: 3d247123 ("drm/msm/a6xx: Add support for using system cache on MMU500 based targets")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Link: https://lore.kernel.org/r/20210424014927.1661-1-jonathan@marek.caSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

@@ -1153,10 +1153,6 @@ static void a6xx_llc_slices_init(struct platform_device *pdev,
 {
 	struct device_node *phandle;
 
-	a6xx_gpu->llc_mmio = msm_ioremap(pdev, "cx_mem", "gpu_cx");
-	if (IS_ERR(a6xx_gpu->llc_mmio))
-		return;
-
 	/*
 	 * There is a different programming path for targets with an mmu500
 	 * attached, so detect if that is the case
@@ -1166,6 +1162,11 @@ static void a6xx_llc_slices_init(struct platform_device *pdev,
 		of_device_is_compatible(phandle, "arm,mmu-500"));
 	of_node_put(phandle);
 
+	if (a6xx_gpu->have_mmu500)
+		a6xx_gpu->llc_mmio = NULL;
+	else
+		a6xx_gpu->llc_mmio = msm_ioremap(pdev, "cx_mem", "gpu_cx");
+
 	a6xx_gpu->llc_slice = llcc_slice_getd(LLCC_GPU);
 	a6xx_gpu->htw_llc_slice = llcc_slice_getd(LLCC_GPUHTW);