drm/exynos: decon5433: Fix WINCONx reset value

The only bits that should be preserved in decon_win_set_fmt() is
WINCONx_ENWIN_F. All other bits depends on the selected pixel formats and
are set by the mentioned function.
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos5433_drm_decon.c

@@ -265,7 +265,7 @@ static void decon_win_set_pixfmt(struct decon_context *ctx, unsigned int win,
 	unsigned long val;
 
 	val = readl(ctx->addr + DECON_WINCONx(win));
-	val &= ~WINCONx_BPPMODE_MASK;
+	val &= WINCONx_ENWIN_F;
 
 	switch (fb->format->format) {
 	case DRM_FORMAT_XRGB1555: