msm: qdss: provide an api to force disable qdss sink

Introduce a new api (qdss_disable_sink) that can be called from atomic
or non-atomic context to force disable the current qdss sink(s).

This api will be used as a way to force stop the sink (eg. etb) from
accepting any more trace data and hence avoid being polluted with trace
data that is uninteresting after an event of interest (eg. userspace
process crash) has occured.

Change-Id: I2a474ba9f51275aa3fa77ee35c39149663dfb03c
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>