ASoC: Intel: Skylake: skl-topology: Fix OOPs ib skl_tplg_complete

If dobj->control is not initialized we end up in an OOPs during
skl_tplg_complete:

[   26.553358] BUG: kernel NULL pointer dereference, address:
0000000000000078
[   26.561151] #PF: supervisor read access in kernel mode
[   26.566897] #PF: error_code(0x0000) - not-present page
[   26.572642] PGD 0 P4D 0
[   26.575479] Oops: 0000 [#1] PREEMPT SMP PTI
[   26.580158] CPU: 2 PID: 2082 Comm: udevd Tainted: G         C
5.4.81 #4
[   26.588232] Hardware name: HP Soraka/Soraka, BIOS
Google_Soraka.10431.106.0 12/03/2019
[   26.597082] RIP: 0010:skl_tplg_complete+0x70/0x144 [snd_soc_skl]

Fixes: 2d744ecf ("ASoC: Intel: Skylake: Automatic DMIC format configuration according to information from NHL")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Tested-by: Lukasz Majczak <lma@semihalf.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210121171644.131059-1-ribalda@chromium.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/skylake/skl-topology.c

@@ -3619,15 +3619,16 @@ static void skl_tplg_complete(struct snd_soc_component *component)
 
 	list_for_each_entry(dobj, &component->dobj_list, list) {
 		struct snd_kcontrol *kcontrol = dobj->control.kcontrol;
-		struct soc_enum *se =
-			(struct soc_enum *)kcontrol->private_value;
-		char **texts = dobj->control.dtexts;
+		struct soc_enum *se;
+		char **texts;
 		char chan_text[4];
 
-		if (dobj->type != SND_SOC_DOBJ_ENUM ||
-		    dobj->control.kcontrol->put !=
-		    skl_tplg_multi_config_set_dmic)
+		if (dobj->type != SND_SOC_DOBJ_ENUM || !kcontrol ||
+		    kcontrol->put != skl_tplg_multi_config_set_dmic)
 			continue;
+
+		se = (struct soc_enum *)kcontrol->private_value;
+		texts = dobj->control.dtexts;
 		sprintf(chan_text, "c%d", mach->mach_params.dmic_num);
 
 		for (i = 0; i < se->items; i++) {