msm: mdss: Sanitize overlay kickoff inputs

Overlay kickoff in certain situations can be called without a ctl
attached to the frame buffer device. These situations need to
be captured and logical path should return safely.

CRs-fixed: 619588
Change-Id: Ibee6b59be667b7e5c9841ffb49c67d86bde45026
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>