sound: oss: fix build warning

while building with allyesconfig it was giving a build warning about
unused variable. declare the variable only if the driver is built as a
module.
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/oss/ad1848.c

@@ -2860,6 +2860,7 @@ static struct {
 	{NULL}
 };
 
+#ifdef MODULE
 static struct isapnp_device_id id_table[] = {
 	{	ISAPNP_VENDOR('C','M','I'), ISAPNP_DEVICE(0x0001),
 		ISAPNP_VENDOR('@','@','@'), ISAPNP_FUNCTION(0x0001), 0 },
@@ -2877,6 +2878,7 @@ static struct isapnp_device_id id_table[] = {
 };
 
 MODULE_DEVICE_TABLE(isapnp, id_table);
+#endif
 
 static struct pnp_dev *activate_dev(char *devname, char *resname, struct pnp_dev *dev)
 {