sound: sgio2audio/pdaudiocf/usb-audio: initialize PCM buffer

sound: sgio2audio/pdaudiocf/usb-audio: initialize PCM buffer

commit 3e85fd614c7b6bb7f33bb04a0dcb5a3bfca4c0fe upstream.

When allocating the PCM buffer, use vmalloc_user() instead of vmalloc().
Otherwise, it would be possible for applications to play the previous
contents of the kernel memory to the speakers, or to read it directly if
the buffer is exported to userspace.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>