soundwire: don't program SDW_SCP_BUSCLOCK_SCALE on a unattached Peripheral

soundwire: don't program SDW_SCP_BUSCLOCK_SCALE on a unattached Peripheral

The SDW_SCP_BUSCLOCK_SCALE register will be programmed when the
Peripheral is attached. We can and should skip programming the
SDW_SCP_BUSCLOCK_SCALE register when the Peripheral is unattached.

Fixes: 645291cfe5e5 ("Soundwire: stream: program BUSCLOCK_SCALE")
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Simon Trimmer <simont@opensource.cirrus.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://patch.msgid.link/20260428084612.322701-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>