ALSA: pcm: Revert bufs move in snd_pcm_xfern_frames_ioctl()

When building with clang older than 17 targeting architectures that use
asm goto for their get_user() and put_user(), such as arm64, after
commit f3d233d ("ALSA: pcm: Relax __free() variable declarations"),
there are bogus errors around skipping over a variable declared with the
cleanup attribute:

  sound/core/pcm_native.c:3308:6: error: cannot jump from this asm goto statement to one of its possible targets
          if (put_user(result, &_xfern->result))
              ^
  ...
  arch/arm64/include/asm/uaccess.h:298:2: note: expanded from macro '__put_mem_asm'
          asm goto(
          ^
  sound/core/pcm_native.c:3295:6: note: possible target of asm goto statement
          if (put_user(0, &_xfern->result))
              ^
  ...
  sound/core/pcm_native.c:3300:8: note: jump exits scope of variable with __attribute__((cleanup))
          void *bufs __free(kfree) =
                ^

clang-17 fixed a bug in clang's jump scope checker [1] where all labels
in a function were checked as valid targets for all asm goto instances
in a function, regardless of whether they were actual targets in a
paricular asm goto's provided list of labels.

To workaround this, revert the change done to
snd_pcm_xfern_frames_ioctl() by commit f3d233d ("ALSA: pcm: Relax
__free() variable declarations") to avoid a variable declared with
cleanup from existing between multiple uses of asm goto. There are no
other uses of cleanup in this function so there should be low risk from
moving this variable back to the top of the function.

Link: ClangBuiltLinux/linux#1886 [1]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512190802.i4Jzbcsl-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260106-pcm_native-revert-var-move-free-for-old-clang-v1-1-06a03693423d@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: nathanchance

sound/core/pcm_native.c

@@ -3286,6 +3286,7 @@ static int snd_pcm_xfern_frames_ioctl(struct snd_pcm_substream *substream,
 {
 	struct snd_xfern xfern;
 	struct snd_pcm_runtime *runtime = substream->runtime;
+	void *bufs __free(kfree) = NULL;
 	snd_pcm_sframes_t result;
 
 	if (runtime->state == SNDRV_PCM_STATE_OPEN)
@@ -3297,8 +3298,7 @@ static int snd_pcm_xfern_frames_ioctl(struct snd_pcm_substream *substream,
 	if (copy_from_user(&xfern, _xfern, sizeof(xfern)))
 		return -EFAULT;
 
-	void *bufs __free(kfree) =
-		memdup_array_user(xfern.bufs, runtime->channels, sizeof(void *));
+	bufs = memdup_array_user(xfern.bufs, runtime->channels, sizeof(void *));
 	if (IS_ERR(bufs))
 		return PTR_ERR(bufs);
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)