video: exynos: Fix S6E8AX0 LCD driver build error

Enable S6E8AX0 LCD driver only if LCD_CLASS_DEVICE is a built-in driver.
Else we get the following errors due to missing symbols:
drivers/built-in.o: In function `s6e8ax0_probe':
:(.text+0x51aec): undefined reference to `lcd_device_register'
:(.text+0x51c44): undefined reference to `lcd_device_unregister'

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/exynos/Kconfig

@@ -22,7 +22,8 @@ config EXYNOS_MIPI_DSI
 
 config EXYNOS_LCD_S6E8AX0
 	bool "S6E8AX0 MIPI AMOLED LCD Driver"
-	depends on (EXYNOS_MIPI_DSI && BACKLIGHT_CLASS_DEVICE && LCD_CLASS_DEVICE)
+	depends on EXYNOS_MIPI_DSI && BACKLIGHT_CLASS_DEVICE
+	depends on (LCD_CLASS_DEVICE = y)
 	default n
 	help
 	  If you have an S6E8AX0 MIPI AMOLED LCD Panel, say Y to enable its