ASoC: pcm: allow backend hardware to be freed in pause state

When front-end PCM session is in paused state, back-end PCM
session will be put in paused state as well if given front-end
PCM session is the only client of the given back-end. Then,
even though the application closes front-end PCM session, DPCM
framework will not allow back-end to enter into HW_FREE state,
and hence back-end will never get shutdown completely.

(cherry picked from commit 6479fa2d82c5fa8b756a4755bc84e2ce48dad850)
CRs-fixed: 411089
CRs-fixed: 409894
Signed-off-by: Banajit Goswami <bgoswa@codeaurora.org>

Change-Id: I4d4f856a0401ff96cef98d374c1d12b10e124528
Signed-off-by: Neha Pandey <nehap@codeaurora.org>