drm/tiny/repaper: Drop edp->enabled

Same patch as the mipi-dbi one, atomic tracks this for us already, we
just have to check the right thing.

Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200612160056.2082681-8-daniel.vetter@ffwll.ch