ggml : allow fill node alloc inplace

[CISC]

Allows ggml_fill to effectively be made in place if possible.

[CISC]

So, it looks like this can only inplace a node's parent once:

llama.cpp/ggml/src/ggml-alloc.c

Lines 645 to 649 in 39f9747

	// if the node's data is external, then we cannot re-use it
	if (!ggml_gallocr_is_own(galloc, parent)) {
	AT_PRINTF("not reusing parent %s for %s as %p is external\n", parent->name, node->name, parent->data);
	continue;
	}

llama.cpp/ggml/src/ggml-alloc.c

Lines 601 to 603 in 39f9747

	static bool ggml_gallocr_is_own(ggml_gallocr_t galloc, struct ggml_tensor * t) {
	return ggml_gallocr_hash_get(galloc, t)->allocated;
	}

llama.cpp/ggml/src/ggml-alloc.c

Lines 672 to 673 in 39f9747

	p_hn->allocated = false; // avoid freeing the parent
	view_src_hn->allocated = false;