drm/i915: Fix the incorrect argument for SDVO SET_TV_format command

Otherwise it will cause that S-video output becomes black/white when
switching to other TV format.

http://bugs.freedesktop.org/show_bug.cgi?id=23916



Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Tested-by: Arnold <arnold.erbsloeh@web.de>
Tested-by: Bazin <bazin.cz@gmail.com>
Tested-by: Nigel <nigel_tuck@eircom.net>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>