[mlir][MemRef] Fixed a lit test for assume alignment (#140447)

Fixed a lit test that failed from my previous commit

Author: shay-kl

mlir/test/Integration/Dialect/MemRef/assume-alignment-runtime-verification.mlir

@@ -10,7 +10,7 @@ func.func @main() {
   // This buffer is properly aligned. There should be no error.
   // CHECK-NOT: ^ memref is not aligned to 8
   %alloc = memref.alloca() : memref<5xf64>
-  memref.assume_alignment %alloc, 8 : memref<5xf64>
+  %0 = memref.assume_alignment %alloc, 8 : memref<5xf64>
 
   // Construct a memref descriptor with a pointer that is not aligned to 4.
   // This cannot be done with just the memref dialect. We have to resort to
@@ -28,10 +28,10 @@ func.func @main() {
   %buffer = builtin.unrealized_conversion_cast %10 : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)> to memref<1xf32>
 
   //      CHECK: ERROR: Runtime op verification failed
-  // CHECK-NEXT: "memref.assume_alignment"(%{{.*}}) <{alignment = 4 : i32}> : (memref<1xf32>) -> ()
+  // CHECK-NEXT: %[[ASSUME:.*]] = "memref.assume_alignment"(%{{.*}}) <{alignment = 4 : i32}> : (memref<1xf32>)
   // CHECK-NEXT: ^ memref is not aligned to 4
   // CHECK-NEXT: Location: loc({{.*}})
-  memref.assume_alignment %buffer, 4 : memref<1xf32>
+  %assume = memref.assume_alignment %buffer, 4 : memref<1xf32>
 
   return
 }