Registration fallback does not return device_id

[manuroe]

which may prevent crypto from working on clients that register with this way.

The issue is at:

synapse/synapse/static/client/register/js/register.js

Lines 67 to 69 in 74854a9

	matrixRegistration.onRegistered(
	response.home_server, response.user_id, response.access_token
	);

The login fallback does not have this issue because it returns the raw CS API response:

synapse/synapse/static/client/login/js/login.js

Line 16 in 74854a9

matrixLogin.onLogin(response);

[richvdh]

This is the least of registration fallback's problems (#7676)