ALSA: es1688: add pedantic range checks

Smatch complains that if (dev == SNDRV_CARDS) we're one past the end of
the array.  That's unlikely to happen in real life, I suppose.

Also smatch complains about "strcpy(card->shortname, pcm->name);"
The "pcm->name" buffer is 80 characters and "card->shortname" is 32
characters.  If you follow the call paths it turns out we never actually
use more than 16 characters so it's not a problem.  But anyway, let's
make it easy for people auditing this in the future.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>