tizenaudio-sink/source: Fix crash when access pcm handle

tizenaudio-sink/source: Fix crash when access pcm handle

build_pollfd() trying to access u->pcm_handle at sink_process_msg() at module loading step.
But, sometimes the device wasn't open yet. (e.g factory reset, power on, ...)
Therefore, null access to u->pcm_handle causes crash.
I think device need to be opened prior to starting sink's message handler.

[Version] 5.0.61
[Profile] Common
[Issue Type] Bug fix

Signed-off-by: KimJeongYeon <jeongyeon.kim@samsung.com>
Change-Id: I060319c261176bb46f7b1c0804322d4d8c491071