soundwire: stream: Remove unneeded checks for NULL bus

soundwire: stream: Remove unneeded checks for NULL bus

Version of the code prior to commit d014688eb373 ("soundwire: stream:
remove bus->dev from logs on multiple buses"), used bus->dev in the
error message after do_bank_switch, this necessitated some checking to
ensure the bus pointer was valid. As the code no longer uses bus->dev
said checking is now redundant, so remove it.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20230602101140.2040141-3-ckeepax@opensource.cirrus.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>