msm: mdss: Add hardware revision check

Our gamma interface works with both current hardware revisions,
11 and 11j, although all testing was carried out on 11. As we
don't know about possible future revisions, let's bail out until
correct offsets for panel commands have been added.

Signed-off-by: Paul Reioux <reioux@gmail.com>
msm: mdss: Use workqueue to send panel commands

Sending panel commands is known to be expensive, honor this by
scheduling this task. Also check for panel state and send commands
only when we're actually awake.

These fixes adress bug reports regarding behaviour during boot.