docs: soundwire: fix some identation at stream.rst

docs: soundwire: fix some identation at stream.rst

Currently, sphinx emits one warning on this file:

	Documentation/driver-api/soundwire/stream.rst:522: WARNING: Block quote ends without a blank line; unexpected unindent.

That's due to some extra spaces before the title of a chapter.

Yet, the list afterwards is missing identation.

So, address both issues.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/eddde9f8d121e27d7968b3d747064e16de8bec4f.1599660067.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>