[mlir][NFC] Add missing namespace qualifier to ODS generated code

Use `::mlir::Region` inside array ref for `VariadicRegion`.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D97376

Author: Vladislav Vinogradov

mlir/test/mlir-tblgen/op-decl.td

@@ -76,7 +76,7 @@ def NS_AOp : NS_Op<"a_op", [IsolatedFromAbove, IsolatedFromAbove]> {
 // CHECK:   ::mlir::Operation::result_range getODSResults(unsigned index);
 // CHECK:   ::mlir::Value r();
 // CHECK:   ::mlir::Region &someRegion();
-// CHECK:   ::mlir::MutableArrayRef<Region> someRegions();
+// CHECK:   ::mlir::MutableArrayRef<::mlir::Region> someRegions();
 // CHECK:   ::mlir::IntegerAttr attr1Attr()
 // CHECK:   uint32_t attr1();
 // CHECK:   ::mlir::FloatAttr attr2Attr()

mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp

@@ -1014,8 +1014,8 @@ void OpEmitter::genNamedRegionGetters() {
 
     // Generate the accessors for a variadic region.
     if (region.isVariadic()) {
-      auto *m = opClass.addMethodAndPrune("::mlir::MutableArrayRef<Region>",
-                                          region.name);
+      auto *m = opClass.addMethodAndPrune(
+          "::mlir::MutableArrayRef<::mlir::Region>", region.name);
       m->body() << formatv("  return (*this)->getRegions().drop_front({0});",
                            i);
       continue;