drm/omap: update for interlaced

'struct omap_video_timings' was updated w/ a 'bool interlaced'.  Without
a matching update in omap_connector, this field could have undefined
values from the stack, which isn't quite ideal.

Update the fxns to convert omapdss<->drm timings structs, and zero-init
'struct omap_video_timings' when it is declared on stack to avoid issues
like this in the future.

Signed-off-by: Rob Clark <rob@ti.com>
Reviewed-by: Sumit Semwal <sumit.semwal@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>