[mlir][acc] Remove declare attribute verification (llvm#137676)

The part that verifies the declare attributes are preserved in the
verifier can fail easily during the FIR lowering pipeline. For example,
during FIR lowering to FIRCG, fir.declare can be removed. Thus, any
fir.declare that has acc.declare attributes will cause a verifier
failure. Since the declare attribute only existed to simplify the effort
of locating acc declare enter and exit points, which can be easily
replaced by a def-use chain traversal, we are considering removing the
verification of declare attributes in this MR.

Example:

```  
%1 = fir.alloca !fir.array<10xf32> {bindc_name = "arr", uniq_name = "_QMmmFsubEarr"}                                                                                                                                  
%2 = fir.shape %c10 : (index) -> !fir.shape<1>
%3 = fir.declare %1(%2) {acc.declare = #acc.declare<dataClause =  acc_create>, uniq_name = "_QMmmFsubEarr"} : (!fir.ref<!fir.array<10xf32>>, !fir.shape<1>) -> !fir.ref<!fir.array<10xf32>>
%4 = acc.create varPtr(%3 : !fir.ref<!fir.array<10xf32>>) -> !fir.ref<!fir.array<10xf32>> {name = "arr"}
%5 = acc.declare_enter dataOperands(%4 : !fir.ref<!fir.array<10xf32>>) 
```

the acc.declare_enter itself is enough to identify when the data region
starts.

Author: SusanTan

mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp

@@ -2910,32 +2910,6 @@ checkDeclareOperands(Op &op, const mlir::ValueRange &operands,
     assert(dataClauseOptional.has_value() &&
            "declare operands can only be data entry operations which must have "
            "dataClause");
-
-    // If varPtr has no defining op - there is nothing to check further.
-    if (!var.getDefiningOp())
-      continue;
-
-    // Check that the varPtr has a declare attribute.
-    auto declareAttribute{
-        var.getDefiningOp()->getAttr(mlir::acc::getDeclareAttrName())};
-    if (!declareAttribute)
-      return op.emitError(
-          "expect declare attribute on variable in declare operation");
-
-    auto declAttr = mlir::cast<mlir::acc::DeclareAttr>(declareAttribute);
-    if (declAttr.getDataClause().getValue() != dataClauseOptional.value())
-      return op.emitError(
-          "expect matching declare attribute on variable in declare operation");
-
-    // If the variable is marked with implicit attribute, the matching declare
-    // data action must also be marked implicit. The reverse is not checked
-    // since implicit data action may be inserted to do actions like updating
-    // device copy, in which case the variable is not necessarily implicitly
-    // declare'd.
-    if (declAttr.getImplicit() &&
-        declAttr.getImplicit() != acc::getImplicitFlag(operand.getDefiningOp()))
-      return op.emitError(
-          "implicitness must match between declare op and flag on variable");
   }
 
   return success();