drm/bridge/sii8620: add Kconfig dependency on extcon

The driver can work with or without extcon framework, but if extcon is
build as module, sii8620 should be build as module as well.

Fixes: 6888384 ("drm/bridge/sii8620: use micro-USB cable detection logic to detect MHL")
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Andrzej Hajda <[email protected]>
Reviewed-by: Chanwoo Choi <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Sean Paul <[email protected]>

Author: Andrzej Hajda

drivers/gpu/drm/bridge/Kconfig

@@ -74,6 +74,7 @@ config DRM_SIL_SII8620
 	tristate "Silicon Image SII8620 HDMI/MHL bridge"
 	depends on OF && RC_CORE
 	select DRM_KMS_HELPER
+	imply EXTCON
 	help
 	  Silicon Image SII8620 HDMI/MHL bridge chip driver.