[media] vsp1: Fix a sparse warning

As reported by: kbuild test robot <fengguang.wu@intel.com>:
	 drivers/media/platform/vsp1/vsp1_drv.c:434:21: sparse: cast removes address space of expression

	   433		vsp1->mmio = devm_ioremap_resource(&pdev->dev, io);
	 > 434		if (IS_ERR((void *)vsp1->mmio))
	 > 435			return PTR_ERR((void *)vsp1->mmio);

There's no need to convert it to void *.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>