ALSA: pci: echoaudio: remove usage of dimen menber of elem_value structure

ALSA: pci: echoaudio: remove usage of dimen menber of elem_value structure

In a couple of years ago, 'echomixer' userspace application was revised
not to use 'dimen' member of 'struct snd_ctl_elem_info'.

This commit removes usage of 'dimen' member from echoaudio PCI driver so
that no implementation uses the member.

Reference: 275353bb684e ("ALSA: echoaudio: purge contradictions between dimension matrix members and total number of members")
Reference: 51db452df07b ("Revert "ALSA: echoaudio: purge contradictions between dimension matrix members and total number of members")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191223023921.8151-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>