ALSA: asound.h - use SNDRV_CTL_ELEM_ID_NAME_MAXLEN

we have defined SNDRV_CTL_ELEM_ID_NAME_MAXLEN as size of name array so use
this define instead of numeric value

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>