ASoC: SOF: topology: Fix null pointer dereference

The "get_function_tplg_files" function is only applicable to
ACPI-based devices (sof_pdata->machine and not sof_pdata->of_machine).
Skip this check for OF-based devices to avoid a NULL pointer
dereference in snd_sof_load_topology().

Fixes: 6d5997c ("ASoC: SOF: topology: load multiple topologies")
Reviewed-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
Reviewed-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Julien Massot <julien.massot@collabora.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://patch.msgid.link/20250429-fixup-of-sof-topology-v4-1-ff692244d64c@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Julien Massot

sound/soc/sof/topology.c

@@ -2481,7 +2481,7 @@ int snd_sof_load_topology(struct snd_soc_component *scomp, const char *file)
 	if (!tplg_files)
 		return -ENOMEM;
 
-	if (sof_pdata->machine->get_function_tplg_files) {
+	if (sof_pdata->machine && sof_pdata->machine->get_function_tplg_files) {
 		tplg_cnt = sof_pdata->machine->get_function_tplg_files(scomp->card,
 								       sof_pdata->machine,
 								       tplg_filename_prefix,