msm: mdss: add async support for hw cursor

Reduce dependency between hw cursor updates and display commit.
Configure the cursor pipes and flush immediately, rather than
waiting for the commit. This would enable multiple cursor updates
within a single vsync. However, the screen update would happen
only after vsync, which would pick the latest cursor update. The
restriction is that after the first cursor update, a display commit
is required to stage the cursor pipes.

Change-Id: I666856c88b8e2decac6578237e9b93b106378ffa
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>