sound: usb: Fix incorrect type assignments

Change the map_pcm_format() helper to return a snd_pcm_format_t
instead of a plain int to fix the following sparse warnings:

 sound/usb/usb_audio_qmi_svc.c:1135:26: expected restricted
  snd_pcm_format_t [usertype] pcm_format
	subs->pcm_format = pcm_format;

 sound/usb/usb_audio_qmi_svc.c:1135:26: got int [assigned] pcm_format
	subs->pcm_format = pcm_format;

 sound/usb/usb_audio_qmi_svc.c:1135:26: warning: incorrect type in
  assignment (different base types)
	subs->pcm_format = pcm_format;

 sound/usb/usb_audio_qmi_svc.c:962:24: expected int
		return SNDRV_PCM_FORMAT_S8;

 sound/usb/usb_audio_qmi_svc.c:962:24: got restricted snd_pcm_format_t
  [usertype]
		return SNDRV_PCM_FORMAT_S8;

 sound/usb/usb_audio_qmi_svc.c:962:24: warning: incorrect type in return
  expression (different base types)
		return SNDRV_PCM_FORMAT_S8;

... and so on.

For these warnings:

 sound/usb/usb_audio_qmi_svc.c:559:47: expected unsigned short
  [usertype] usb_audio_spec_revision
		resp->usb_audio_spec_revision =

 sound/usb/usb_audio_qmi_svc.c:559:47: got restricted __le16 [usertype]
  bcdADC
		resp->usb_audio_spec_revision =

 sound/usb/usb_audio_qmi_svc.c:559:47: warning: incorrect type in
  assignment (different base types)
		resp->usb_audio_spec_revision =

Fix these by passing the bcdADC value through le16_to_cpu before
assigning to the usb_audio_spec_revision member.

Change-Id: I0be5848846be7e29566a7854c5190634bce4347d
Signed-off-by: Jack Pham <jackp@codeaurora.org>