ASoC: core: Check for rtd == NULL in snd_soc_remove_pcm_runtime()

ASoC: core: Check for rtd == NULL in snd_soc_remove_pcm_runtime()

snd_soc_remove_pcm_runtime() might be called with rtd == NULL which will
leads to null pointer dereference.
This was reproduced with topology loading and marking a link as ignore
due to missing hardware component on the system.
On module removal the soc_tplg_remove_link() would call
snd_soc_remove_pcm_runtime() with rtd == NULL since the link was ignored,
no runtime was created.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://patch.msgid.link/20250619084222.559-3-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>