drm/omap: fix display SYNC/DE flags

drm/omap: fix display SYNC/DE flags

At the moment VSYNC/HSYNC/DE high/low flags set by the panel/encoder
drivers get lost when the videotimings are translated to DRM's
videomode, as DRM's mode does not have corresponding flags.

DRM has bus-flags for this purpose, and while it lacks a few flags at
the moment, it should be used here. However, until we rewrite omapdrm's
device model, using bus-flags is rather difficult.

As a short term fix, this patch makes sure that every time the videomode
is set in omap_crtc_mode_set_nofb(), the driver asks for the SYNC/DE
flags from the panel/encoder drivers, and thus we get the correct flags
into use.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>