Revert "Don't run VectorizeLoop pass on custom datatypes"

This reverts commit 9bd17934c3914889fed97acd56cf1d13e39c9f42.
We don't need this anymore due to the change made by Logan Weber to add a
SkipVectorize pass (apache#3222).

src/pass/vectorize_loop.cc

@@ -29,7 +29,6 @@
 #include <unordered_map>
 #include <vector>
 #include "../arithmetic/compute_expr.h"
-#include "../codegen/datatype/registry.h"
 
 namespace tvm {
 namespace ir {
@@ -103,13 +102,6 @@ class Vectorizer : public IRMutator {
   // user mutate from parent.
   using IRMutator::Mutate;
 
-  // Don't run on custom datatypes.
-  Expr Mutate(Expr expr) final {
-    if (tvm::datatype::Registry::Global()->GetTypeRegistered(expr.type().code()))
-      return expr;
-    return IRMutator::Mutate(expr);
-  }
-
   Stmt Mutate(Stmt stmt) final {
     CHECK(!need_scalarize_);