[media] exynos-gsc: Fix compilation warning

Used type casting to avoid the following compilation warning:
drivers/media/platform/exynos-gsc/gsc-core.c:983:37: warning:
incorrect type in assignment (different modifiers)
drivers/media/platform/exynos-gsc/gsc-core.c:983:37:
expected struct gsc_driverdata *driver_data
drivers/media/platform/exynos-gsc/gsc-core.c:983:37:
got void const *data

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/exynos-gsc/gsc-core.c

@@ -980,7 +980,7 @@ static void *gsc_get_drv_data(struct platform_device *pdev)
 		match = of_match_node(of_match_ptr(exynos_gsc_match),
 					pdev->dev.of_node);
 		if (match)
-			driver_data =  match->data;
+			driver_data = (struct gsc_driverdata *)match->data;
 	} else {
 		driver_data = (struct gsc_driverdata *)
 			platform_get_device_id(pdev)->driver_data;