Migrate CONFIG_BOOTCOUNT_ALEN to Kconfig

Convert CONFIG_BOOTCOUNT_ALEN to Kconfig
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
diff --git a/drivers/bootcount/Kconfig b/drivers/bootcount/Kconfig
index 9fde2f2..c41b131 100644
--- a/drivers/bootcount/Kconfig
+++ b/drivers/bootcount/Kconfig
@@ -64,7 +64,6 @@
 	  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
 
 config BOOTCOUNT_AT91
 	bool "Boot counter for Atmel AT91SAM9XE"
@@ -72,6 +71,14 @@
 
 endchoice
 
+config BOOTCOUNT_ALEN
+	int "I2C address length"
+	default 1
+	depends on BOOTCOUNT_I2C
+	help
+	  Length of the the I2C address at SYS_BOOTCOUNT_ADDR for storing
+	  the boot counter.
+
 config SYS_BOOTCOUNT_SINGLEWORD
 	bool "Use single word to pack boot count and magic value"
 	depends on BOOTCOUNT_GENERIC