msm: synx: redesign callback registration and dispatch

The changes modify the callback registration and dispatch
on a synx object for non-blocking wait.
The userspace callback payloads are maintained in UMD driver
and unique id passed by client is saved in callback entry
to manage the callback. These callbacks are distinguished
with the callbacks registered by kernel clients through the
default callback function registered.
This provides uniform handling (in most cases) for callbacks
registered by userspace and kernel clients.
The change also allows signaling with CANCELLED state.

Change-Id: Ic084374c63c3c09c5deccb404e81da69f1dcb70e
Signed-off-by: Sumukh Hallymysore Ravindra <shallymy@codeaurora.org>