ALSA: emu10k1: add error handling for snd_ctl_add

When snd_ctl_add fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling snd_ctl_add.
Signed-off-by: NZhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/emu10k1/emupcm.c

@@ -1858,7 +1858,9 @@ int snd_emu10k1_pcm_efx(struct snd_emu10k1 *emu, int device)
 	if (!kctl)
 		return -ENOMEM;
 	kctl->id.device = device;
-	snd_ctl_add(emu->card, kctl);
+	err = snd_ctl_add(emu->card, kctl);
+	if (err < 0)
+		return err;
 
 	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, snd_dma_pci_data(emu->pci), 64*1024, 64*1024);