msm: kgsl: Keep the timeline fence valid for logging

The timeline fence needs to remain valid for logging purposes. Take an
extra refcount on the timeline dma_fence to make sure it doesn't go
away till we're done with it.

Change-Id: I6670ef7add099a72684c1fe20ed009dff85d1f27
Signed-off-by: Lynus Vaz <quic_lvaz@quicinc.com>