ALSA: hda/ca0132: minor fix for allocation size

ALSA: hda/ca0132: minor fix for allocation size

Although the "dma_chan" pointer occupies more or equal space compared
to "*dma_chan", the allocation size should use the size of variable
itself.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 01ef7dbffb41 ("ALSA: hda - Update CA0132 codec to load DSP firmware binary")
Signed-off-by: Alexey V. Vissarionov <gremlin@altlinux.org>
Link: https://lore.kernel.org/r/20230117111522.GA15213@altlinux.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>