soundwire: only handle alert events when the peripheral is attached

soundwire: only handle alert events when the peripheral is attached

It doesn't make sense to handle an alert event when the peripheral is
not attached. The slave->status could be SDW_SLAVE_ATTACHED or
SDW_SLAVE_ALERT when it is attached on the bus.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Link: https://patch.msgid.link/20260520025720.1999367-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>