drm/radeon: update comments to clarify VM setup (v2)

The actual set up and assignment of VM page tables
is done on the fly in radeon_gart.c.

v2: update vm size comments

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
diff --git a/drivers/gpu/drm/radeon/ni.c b/drivers/gpu/drm/radeon/ni.c
index 8bcb554..83dc085 100644
--- a/drivers/gpu/drm/radeon/ni.c
+++ b/drivers/gpu/drm/radeon/ni.c
@@ -770,6 +770,10 @@
 	WREG32(0x15DC, 0);
 
 	/* empty context1-7 */
+	/* Assign the pt base to something valid for now; the pts used for
+	 * the VMs are determined by the application and setup and assigned
+	 * on the fly in the vm part of radeon_gart.c
+	 */
 	for (i = 1; i < 8; i++) {
 		WREG32(VM_CONTEXT0_PAGE_TABLE_START_ADDR + (i << 2), 0);
 		WREG32(VM_CONTEXT0_PAGE_TABLE_END_ADDR + (i << 2), 0);