Remove type casting from assignments involving void pointers
in two places in drivers/acpi/video.c.

[rjw: Changelog]
Signed-off-by: NFelipe Contreras <felipe.contreras@gmail.com>
Reviewed-by: NAaron Lu <aaron.lu@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>