ALSA: cs4281: Fix missing chip initialization

The chip variable was forgotten to be initialized properly while
changing the object creation from the own malloc to
card->private_data.  This patch fixes it.

Fixes: 99041fea

 ("ALSA: cs4281: Allocate resources with device-managed APIs")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/s5him14ocjz.wl-tiwai@suse.de


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