drm/exynos/fimd: signal frame done interrupt at front porch

VBLANK interrupt should be signalled as soon as scanout ends, front porch
is the best moment.

Signed-off-by: Andrzej Hajda <[e-mail]>
Signed-off-by: Inki Dae <[e-mail]>

drivers/gpu/drm/exynos/exynos_drm_fimd.c

···
 			val |= VIDINTCON0_INT_FRAME;
 
 			val &= ~VIDINTCON0_FRAMESEL0_MASK;
-			val |= VIDINTCON0_FRAMESEL0_VSYNC;
+			val |= VIDINTCON0_FRAMESEL0_FRONTPORCH;
 			val &= ~VIDINTCON0_FRAMESEL1_MASK;
 			val |= VIDINTCON0_FRAMESEL1_NONE;
 		}