ALSA: HDA: Fix volume control naming for surround speakers on Realtek auto-parser

When more than one pair of internal speakers is present, allow names
according to their channels.

Tested-by: Bartłomiej Żogała <nusch88@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>