ALSA: pcm: Fix avail to return error if stream is suspended

When the stream is in suspended state some applications wait
on "Stream Pipe Error" in response to snd_pcm_avail call to
resume the stream.

In the current implementation snd_pcm_avail() returns zero
when the stream is in suspended state. This causes application
to enter in infinite loop for frames to be available.

"Stream pipe Error" code is getting returned for read/write
call when the stream is in suspended state. Similarly update
snd_pcm_avail to return -ESTRPIPE.

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>