[rebase][OpenMP] Fix simd (until D112526 is merged)

https://reviews.llvm.org/D112526 fixed a SIMD bug that wrongly caused
the change 3rd arg of __kmpc_dispatch_init_4 from 47 to 37 in wsloop-simd.f90
test.

Only reproduce the part required for the fix until https://reviews.llvm.org/D112526
is reviewed and merged and can be cherry-picked and replace this code.

Co-authored-by: Mats Petersson <[email protected]>

Author: jeanPerier

mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp

@@ -286,6 +286,12 @@ parseScheduleClause(OpAsmParser &parser, SmallString<8> &schedule,
     modifiers.push_back(mod);
   }
 
+  // Fix up "only simd specified"
+  if (modifiers.size() == 1 && modifiers[0] == "simd") {
+    modifiers[0] = "none";
+    modifiers.push_back(StringRef("simd"));
+  }
+
   if (parser.parseRParen())
     return failure();