[mlir][spirv] Remove nonlocal call verification.

`spirv.FunctionCall`'s verifier was being too aggressive.
It included verification of non-local properties by
looking at the callee's definition.

This caused problems in cases where callee had verification
errors and could lead to null pointer dereferencing.

According to MLIR's developers guide

  TLDR: only verify local aspects of an operation,
  in particular don’t follow def-use chains
  (don’t look at the producer of any operand or the user
  of any results).

https://mlir.llvm.org/getting_started/DeveloperGuide/#ir-verifier

Author: amd-eochoalo

mlir/lib/Dialect/SPIRV/IR/ControlFlowOps.cpp

@@ -160,42 +160,12 @@ LogicalResult FunctionCallOp::verify() {
            << fnName.getValue() << "' not found in nearest symbol table";
   }
 
-  auto functionType = funcOp.getFunctionType();
-
   if (getNumResults() > 1) {
     return emitOpError(
                "expected callee function to have 0 or 1 result, but provided ")
            << getNumResults();
   }
 
-  if (functionType.getNumInputs() != getNumOperands()) {
-    return emitOpError("has incorrect number of operands for callee: expected ")
-           << functionType.getNumInputs() << ", but provided "
-           << getNumOperands();
-  }
-
-  for (uint32_t i = 0, e = functionType.getNumInputs(); i != e; ++i) {
-    if (getOperand(i).getType() != functionType.getInput(i)) {
-      return emitOpError("operand type mismatch: expected operand type ")
-             << functionType.getInput(i) << ", but provided "
-             << getOperand(i).getType() << " for operand number " << i;
-    }
-  }
-
-  if (functionType.getNumResults() != getNumResults()) {
-    return emitOpError(
-               "has incorrect number of results has for callee: expected ")
-           << functionType.getNumResults() << ", but provided "
-           << getNumResults();
-  }
-
-  if (getNumResults() &&
-      (getResult(0).getType() != functionType.getResult(0))) {
-    return emitOpError("result type mismatch: expected ")
-           << functionType.getResult(0) << ", but provided "
-           << getResult(0).getType();
-  }
-
   return success();
 }