dtc(1): Pull in fix for segfault-upon-error condition

Specifically, parse errors within a node would lead to a segfault due to
an unconditional dereference after emitting the error.

Obtained from:	https://github.com/davidchisnall/dtc/commit/e5ecf9319fd3f
MFC after:	3 days

usr.bin/dtc/fdt.cc

@@ -1622,8 +1622,11 @@ device_tree::parse_file(text_input_buffer &input,
 			}
 			input.next_token();
 			n = node::parse(input, *this, std::move(name), string_set(), string(), &defines);
+			if (n)
+			{
 				n->name_is_path_reference = name_is_path_reference;
 			}
+		}
 		else
 		{
 			input.parse_error("Failed to find root node /.");