status_led: Kconfig migration - introduction

Move all of the status LED feature to drivers/led/Kconfig.
doc/README.LED updated to reflect the Kconfig implementation.

Tested boards: CL-SOM-AM57x, CM-T335

Signed-off-by: Uri Mashiach <uri.mashiach@compulab.co.il>
diff --git a/README b/README
index 7e0dd35..a95348a 100644
--- a/README
+++ b/README
@@ -2033,7 +2033,7 @@
 
 		A byte containing the id of the VLAN.
 
-- Status LED:	CONFIG_STATUS_LED
+- Status LED:	CONFIG_LED_STATUS
 
 		Several configurations allow to display the current
 		status using a LED. For instance, the LED will blink
@@ -2041,15 +2041,15 @@
 		soon as a reply to a BOOTP request was received, and
 		start blinking slow once the Linux kernel is running
 		(supported by a status LED driver in the Linux
-		kernel). Defining CONFIG_STATUS_LED enables this
+		kernel). Defining CONFIG_LED_STATUS enables this
 		feature in U-Boot.
 
 		Additional options:
 
-		CONFIG_GPIO_LED
+		CONFIG_LED_STATUS_GPIO
 		The status LED can be connected to a GPIO pin.
 		In such cases, the gpio_led driver can be used as a
-		status LED backend implementation. Define CONFIG_GPIO_LED
+		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
 		to include the gpio_led driver in the U-Boot binary.
 
 		CONFIG_GPIO_LED_INVERTED_TABLE