Convert CONFIG_BOOTCOUNT_I2C to Kconfig

This converts the following to Kconfig:
  CONFIG_BOOTCOUNT_I2C

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
diff --git a/drivers/bootcount/Kconfig b/drivers/bootcount/Kconfig
index eabfd13..8c19ae6 100644
--- a/drivers/bootcount/Kconfig
+++ b/drivers/bootcount/Kconfig
@@ -46,6 +46,15 @@
 	  Store the bootcount in DRAM protected against against bit errors
 	  due to short power loss or holding a system in RESET.
 
+config BOOTCOUNT_I2C
+	bool "Boot counter on I2C device"
+	help
+	  Enable support for the bootcounter on an i2c (like RTC) device.
+	  CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
+	  CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
+	                              the bootcounter.
+	  CONFIG_BOOTCOUNT_ALEN = address len
+
 endchoice
 
 config SYS_BOOTCOUNT_SINGLEWORD