py: Merge BINARY_OP_SUBSCR and store_subscr (w/ delete) into subscr.

mp_obj_t->subscr now does load/store/delete.
diff --git a/py/showbc.c b/py/showbc.c
index d755d3c..bf25966 100644
--- a/py/showbc.c
+++ b/py/showbc.c
@@ -182,6 +182,10 @@
                 printf("LOAD_BUILD_CLASS");
                 break;
 
+            case MP_BC_LOAD_SUBSCR:
+                printf("LOAD_SUBSCR");
+                break;
+
             case MP_BC_STORE_FAST_0:
                 printf("STORE_FAST_0");
                 break;