OMAPFB: Do not suspend on FB BLANK, instead disable panel

We do not have state notifiers on panel suspend/resume, so Android is
not notified if display is suspended in FB BLANK.  Panels should only
suspend as part of a system wide suspend, where early suspend handlers
are called.

Luckily panel suspend and panel disable methods are identical.

Change-Id: Ifc93ffff8cd794736175622bf63e80266f55ec8d
Signed-off-by: Lajos Molnar <lajos@ti.com>