drm/msm/sde: fix race condition between enable/disable events

When crtc event disable api is called, we search for the node with spin
lock to avoid race condition in traversing list with other
threads.Currently driver should remove the node with spin lock held
before freeing the node to avoid list corruption.

Change-Id: Iece8678c92e4bd6ed858e3e5174682fa01b28a0f
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>