msm: kgsl: Add enable_signaling for timeline fence

Implement enable_signaling for timeline fence. Dma fence driver's
APIs such as dma_fence_add_callback() use enable_signaling for
fence status and correct return value. Implementing this fix
scenarios such as dma_fence_add_callback() returning invalid
return value when timeline has been moved ahead.

Change-Id: Iaad8bf2801802216050e70c1b8ee1e0b2ec87a5f
Signed-off-by: Pranav Patel <pranavp@codeaurora.org>