ASoC: pcm: change playback_active to unsigned int

In combo usecase there are 2 front-end dai's with
same codec dai. Using a single bit as the counter
causes the counter to roll over to 0 during combo usecase.
To resolve this change counter to unsigned int from single bit.

CRs-Fixed: 1049348
Change-Id: I196802e6d23a9292ff2915c1b4b61c2b3ead9fa8
Signed-off-by: Vidyakumar Athota <vathota@codeaurora.org>