pcm: fix minor bug in ioctl

alsa-project/alsa-lib pull request #330 was opened from dancrossnyc:

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 #329

Request URL : https://github.com/alsa-project/alsa-lib/pull/330 Patch URL : https://github.com/alsa-project/alsa-lib/pull/330.patch Repository URL: https://github.com/alsa-project/alsa-lib