ALSA: hda - Clean up the code to check bdl_pos_adj option

Just a minor cleanup; instead of passing an array, pass the assigned
bdl_pos_adj option value directory in struct azx.  Also split the code
to get the default bdl_pos_adj value for the change that will follow
after this.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_controller.h b/sound/pci/hda/hda_controller.h
index c1d28a6..a32ec90 100644
--- a/sound/pci/hda/hda_controller.h
+++ b/sound/pci/hda/hda_controller.h
@@ -147,7 +147,7 @@
 #endif
 
 	/* flags */
-	const int *bdl_pos_adj;
+	int bdl_pos_adj;
 	int poll_count;
 	unsigned int running:1;
 	unsigned int single_cmd:1;