ALSA: Add #ifdef CONFIG_PCI guard for snd_pci_quirk_* functions

This fixes below build warning when CONFIG_PCI is not set.

CC      sound/sound_core.o
In file included from sound/sound_core.c:15:
include/sound/core.h:454: warning: 'struct pci_dev' declared inside parameter list
include/sound/core.h:454: warning: its scope is only this definition or declaration, which is probably not what you want

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/core.h b/include/sound/core.h
index 5ab255f..cea1b54 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -417,6 +417,7 @@
 #define gameport_get_port_data(gp) (gp)->port_data
 #endif
 
+#ifdef CONFIG_PCI
 /* PCI quirk list helper */
 struct snd_pci_quirk {
 	unsigned short subvendor;	/* PCI subvendor ID */
@@ -456,5 +457,6 @@
 const struct snd_pci_quirk *
 snd_pci_quirk_lookup_id(u16 vendor, u16 device,
 			const struct snd_pci_quirk *list);
+#endif
 
 #endif /* __SOUND_CORE_H */