Boot: integrate MCUBoot with TF-M to act as a BL2 bootloader

Modifications in MCUBoot to be aligned with BL2 requirements in TF-M:
 -- OS dependency was removed, no need to copy any OS repo to build it
 -- CMSIS serial driver is used
 -- flash driver interface is aligned with original version
 -- S and NS images are handeled as a single binary blob
 -- automatic image concatenation and signing at build time
 -- authentication based on SHA256 and RSA-2048 digital signature
 -- mbedTLS library is used for cryptographic operation
 -- static analyser warnings fixed in some files

Change-Id: I54891762eac8d0df634e954ff19a9505b16f3028
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 90d1d70..1b6d722 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,6 +11,7 @@
 include("Common/BuildSys")
 
 add_subdirectory(app)
+add_subdirectory(bl2/ext/mcuboot)
 
 #Define a top-level generic tfm project
 project(tfm LANGUAGES)