extcon: Add an API to get extcon device from dt node

Added an API of_extcon_get_extcon_dev() to be used by drivers to get
extcon device in the case of dt boot (this can be used instead of
extcon_get_extcon_dev()).

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
index 540e2c3..759fdae 100644
--- a/drivers/extcon/Makefile
+++ b/drivers/extcon/Makefile
@@ -2,6 +2,8 @@
 # Makefile for external connector class (extcon) devices
 #
 
+obj-$(CONFIG_OF_EXTCON)		+= of_extcon.o
+
 obj-$(CONFIG_EXTCON)		+= extcon-class.o
 obj-$(CONFIG_EXTCON_GPIO)	+= extcon-gpio.o
 obj-$(CONFIG_EXTCON_ADC_JACK)	+= extcon-adc-jack.o