ASoC: SOF: Fix NULL pointer exception in sof_pci_probe callback

We are accessing "desc->ops" in sof_pci_probe without checking "desc"
pointer. This results in NULL pointer exception if pci_id->driver_data
i.e desc pointer isn't defined in sof device probe:

BUG: kernel NULL pointer dereference, address: 0000000000000060
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
RIP: 0010:sof_pci_probe+0x1e/0x17f [snd_sof_pci]
Code: Unable to access opcode bytes at RIP 0xffffffffc043dff4.
RSP: 0018:ffffac4b03b9b8d8 EFLAGS: 00010246

Add NULL pointer check for sof_dev_desc pointer to avoid such exception.
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Ajit Kumar Pandey <AjitKumar.Pandey@amd.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220426183357.102155-1-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-pci-dev.c

@@ -153,6 +153,11 @@ int sof_pci_probe(struct pci_dev *pci, const struct pci_device_id *pci_id)
 
 	dev_dbg(&pci->dev, "PCI DSP detected");
 
+	if (!desc) {
+		dev_err(dev, "error: no matching PCI descriptor\n");
+		return -ENODEV;
+	}
+
 	if (!desc->ops) {
 		dev_err(dev, "error: no matching PCI descriptor ops\n");
 		return -ENODEV;