Added trait NoMemoryEffect to assume_alignment

Assume_alignment has no trait which specifies how it interacts with
memory, this causes an issue in OwnershipBasedBufferDeallocation,
which require all operations which operate on buffers to have explicit
traits defining how the operation interacts with memory.

To prevent this error, I changed assume_alignment to include the trait
NoMemoryEffect. This is valid because assume_alignment is an assertion
for optimization purposes only; it does not allocate, free, read, or
write memory, nor does it change program semantics or memory state.

Author: Shay Kleiman

mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td

@@ -142,7 +142,7 @@ class AllocLikeOp<string mnemonic,
 // AssumeAlignmentOp
 //===----------------------------------------------------------------------===//
 
-def AssumeAlignmentOp : MemRef_Op<"assume_alignment"> {
+def AssumeAlignmentOp : MemRef_Op<"assume_alignment", [NoMemoryEffect]> {
   let summary =
       "assertion that gives alignment information to the input memref";
   let description = [{