msm: mdss: Handle ping pong split configuration in splash done

After continuous splash reconfiguration, when turning off the
clocks ping pong split configuration is not handled properly.
Pingpong split uses single controller and dual context, so
the second context of the same controller should be used
instead of the slave controller.

Change-Id: Ibafdfd0aba4e0f02f141d60cb8866f353137a3ce
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>
Signed-off-by: Abhijith Desai <desaia@codeaurora.org>