ALSA: hda: generic: Remove redundant assignment to dac

Variable dac is set to zero, but this value is never read as it is
overwritten or not used later on, hence it is a redundant assignment
and can be removed.

Clean up the following clang-analyzer warning:

sound/pci/hda/hda_generic.c:1436:4: warning: Value stored to 'dac' is
never read [clang-analyzer-deadcode.DeadStores].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/1620904271-76027-1-git-send-email-jiapeng.chong@linux.alibaba.com


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