ALSA: es1938: Convert to the new PCM copy ops

Replace the copy ops with the new copy_user and copy_kernel ops.
It's used only for a capture stream (for some hardware workaround),
thus we need no silence operation.

Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>