ALSA: ctl: remove unused macro for timestamping of elem_value

In a former commit, 'tstamp' member was removed from 'struct
snd_ctl_elem_value' in a middle way toward solution of Y2038 issue. In a
protocol of ALSA control interface, this member is designed to deliver
timestamp information in the value structure when the target element
supports SNDRV_CTL_ELEM_ACCESS_TIMESTAMP flag.

Actually, the feature is neither used by kernel space nor user space,
especiall alsa-lib has no API for the feature. Therefore it's reasonable
to remove both of them. Practically, the timestamp information
corresponds to no information about type of clock ID. It can bring
confusions to applications.

Reference: a4e7dd35 ("ALSA: Avoid using timespec for struct snd_ctl_elem_value")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191223023921.8151-2-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/asound.h

@@ -974,7 +974,7 @@ typedef int __bitwise snd_ctl_elem_iface_t;
 #define SNDRV_CTL_ELEM_ACCESS_WRITE		(1<<1)
 #define SNDRV_CTL_ELEM_ACCESS_READWRITE		(SNDRV_CTL_ELEM_ACCESS_READ|SNDRV_CTL_ELEM_ACCESS_WRITE)
 #define SNDRV_CTL_ELEM_ACCESS_VOLATILE		(1<<2)	/* control value may be changed without a notification */
-#define SNDRV_CTL_ELEM_ACCESS_TIMESTAMP		(1<<3)	/* when was control changed */
+// (1 << 3) is unused.
 #define SNDRV_CTL_ELEM_ACCESS_TLV_READ		(1<<4)	/* TLV read is possible */
 #define SNDRV_CTL_ELEM_ACCESS_TLV_WRITE		(1<<5)	/* TLV write is possible */
 #define SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE	(SNDRV_CTL_ELEM_ACCESS_TLV_READ|SNDRV_CTL_ELEM_ACCESS_TLV_WRITE)