drm/nv50: use a slightly different initial context for nv96

I'm not 100% sure that the nv94 one we were using won't work.  The context
layouts are identical (well.. same ctxprog, so of course!), only a couple
of registers differ.  But, be safe until we actually get some 9xxx chips
working.

shared-core/nv50_graph.c

@@ -198,9 +198,11 @@ nv50_graph_create_context(struct nouveau_channel *chan)
 		ctxvals = nv92_ctxvals;
 		break;
 	case 0x94:
-	case 0x96:
 		ctxvals = nv94_ctxvals;
 		break;
+	case 0x96:
+		ctxvals = nv96_ctxvals;
+		break;
 	case 0xaa:
 		ctxvals = nvaa_ctxvals;
 		break;