pcm: hw: fix minor bug in sw_params ioctl

pcm: hw: fix minor bug in sw_params ioctl

Commit 2115cdb added a new call to the `SNDRV_PCM_IOCTL_SW_PARAMS`
ioctl on line 675 of src/pcm/pcm_hw.c, but passed the `sw_params`
argument by value; this should be passed by pointer.

I ran across this in the context of the direwolf software modem
for amateur radio; debugging details are in
https://groups.io/g/direwolf/message/8286

Fixes: https://github.com/alsa-project/alsa-lib/pull/330
Signed-off-by: Dan Cross <cross@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>