drm/msm/gpu: Add a comment in a6xx_gmu_init()

If you don't realize is_a650_family() also encompasses a660 family,
you'd think that the debug buffer is double allocated.  Add a comment
to make this more clear.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20211124214151.1427022-11-robdclark@gmail.comSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a6xx_gmu.c

@@ -1527,6 +1527,7 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 	if (ret)
 		goto err_memory;
 
+	/* Note that a650 family also includes a660 family: */
 	if (adreno_is_a650_family(adreno_gpu)) {
 		ret = a6xx_gmu_memory_alloc(gmu, &gmu->icache,
 			SZ_16M - SZ_16K, 0x04000);
@@ -1543,6 +1544,8 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 		if (ret)
 			goto err_memory;
 	} else {
+		BUG_ON(adreno_is_a660_family(adreno_gpu));
+
 		/* HFI v1, has sptprac */
 		gmu->legacy = true;