bootcount: add support for bootcounter on EXT filesystem

Add support for bootcounter on an EXT filesystem.
Sync configuration whitelist.

Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
diff --git a/drivers/bootcount/Makefile b/drivers/bootcount/Makefile
index ed9659a..45445d2 100644
--- a/drivers/bootcount/Makefile
+++ b/drivers/bootcount/Makefile
@@ -9,3 +9,4 @@
 obj-$(CONFIG_BOOTCOUNT_RAM)	+= bootcount_ram.o
 obj-$(CONFIG_BOOTCOUNT_ENV)	+= bootcount_env.o
 obj-$(CONFIG_BOOTCOUNT_I2C)	+= bootcount_i2c.o
+obj-$(CONFIG_BOOTCOUNT_EXT)	+= bootcount_ext.o