ALSA: line6: Handle impulse response via control API

Instead of sysfs and the conditional build with Kconfig, implement the
handling of the impulse response controls via control API, and always
enable the build.  Two new controls, "Impulse Response Volume" and
"Impulse Response Period" are added as a replacement for the former
sysfs files.

Tested-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/playback.c

@@ -60,8 +60,6 @@ static void change_volume(struct urb *urb_out, int volume[],
 	}
 }
 
-#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
-
 /*
 	Create signal for impulse response test.
 */
@@ -105,8 +103,6 @@ static void create_impulse_test_signal(struct snd_line6_pcm *line6pcm,
 	}
 }
 
-#endif
-
 /*
 	Add signal to buffer for software monitoring.
 */
@@ -243,7 +239,6 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 	change_volume(urb_out, line6pcm->volume_playback, bytes_per_frame);
 
 	if (line6pcm->prev_fbuf != NULL) {
-#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
 		if (line6pcm->flags & LINE6_BITS_PCM_IMPULSE) {
 			create_impulse_test_signal(line6pcm, urb_out,
 						   bytes_per_frame);
@@ -257,7 +252,6 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 					urb_out->transfer_buffer_length);
 			}
 		} else {
-#endif
 			if (!
 			    (line6pcm->line6->
 			     properties->capabilities & LINE6_CAP_HWMON)
@@ -266,9 +260,7 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 				add_monitor_signal(urb_out, line6pcm->prev_fbuf,
 						   line6pcm->volume_monitor,
 						   bytes_per_frame);
-#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
 		}
-#endif
 	}
 
 	ret = usb_submit_urb(urb_out, GFP_ATOMIC);