docs: soundwire: locking: fix tags for a code-block

There's an ascii artwork at Example 1 whose code-block is not properly
idented, causing those warnings.

    Documentation/driver-api/soundwire/locking.rst:50: WARNING: Inconsistent literal block quoting.
    Documentation/driver-api/soundwire/locking.rst:51: WARNING: Line block ends without a blank line.
    Documentation/driver-api/soundwire/locking.rst:55: WARNING: Inline substitution_reference start-string without end-string.
    Documentation/driver-api/soundwire/locking.rst:56: WARNING: Line block ends without a blank line.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>