ALSA: timer: Constify snd_timer_hardware definitions

Most of snd_timer_hardware definitions do simply copying to another
struct as-is.  Mark them as const for further optimization.

There should be no functional changes by this patch.

Link: https://lore.kernel.org/r/20200103081714.9560-21-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>