Boot: Introduce rollback protection

- Add image security counter verification (read image security counter
  from the manifest and compare it against the stored security counter)
  as a mandatory part of the image validation process.
- Store the newest value of security counter in a non-volatile (NV)
  counter.
- Add security counter interface to MCUBoot.

Change-Id: I608508e707d01c3777788bc754810407fae610e2
Signed-off-by: David Vincze <david.vincze@arm.com>
diff --git a/bl2/ext/mcuboot/bootutil/src/bootutil_priv.h b/bl2/ext/mcuboot/bootutil/src/bootutil_priv.h
index 918d2d1..1eb5a4a 100644
--- a/bl2/ext/mcuboot/bootutil/src/bootutil_priv.h
+++ b/bl2/ext/mcuboot/bootutil/src/bootutil_priv.h
@@ -44,6 +44,7 @@
 #define BOOT_EBADSTATUS 5
 #define BOOT_ENOMEM     6
 #define BOOT_EBADARGS   7
+#define BOOT_EBADMAGIC  8
 
 #define BOOT_TMPBUF_SZ  256