Fix running newtmgr when building for mcuboot

This enables mynewt to use mcuboot as a remote repository, which is only
required when using newtmgr to manage images. Since mcuboot has slightly
changed the trailer format, newtmgr built against the bundled mynewt
bootloader writes the magic and flags to the wrong location.

To build a mynewt app the wants to run with mcuboot as the bootloader
and requires newtmgr one needs to change the app's pkg.yml dependencies
as follows:

-    - boot/bootutil
+    - "@mcuboot/boot/bootutil"

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/mynewt/pkg.yml b/boot/mynewt/pkg.yml
index 0c55674..1d563b8 100644
--- a/boot/mynewt/pkg.yml
+++ b/boot/mynewt/pkg.yml
@@ -26,6 +26,7 @@
     - loader
 
 pkg.deps:
+    - "@mcuboot/boot/mynewt/mcuboot_config"
     - "@mcuboot/boot/bootutil"
     - "@apache-mynewt-core/kernel/os"
     - "@apache-mynewt-core/sys/console/stub"