Bump version to 2.1.2

Yotta version bumped to 2.1.3, as we had to do one more patch release to the
yotta registry to accommodate for dependencies updates.
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index e5cd908..27b5d4b 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -28,7 +28,7 @@
 # identify the project. Note that if you do not use Doxywizard you need
 # to put quotes around the project name if it contains spaces.
 
-PROJECT_NAME           = "mbed TLS v2.1.1"
+PROJECT_NAME           = "mbed TLS v2.1.2"
 
 # The PROJECT_NUMBER tag can be used to enter a project or revision number.
 # This could be handy for archiving the generated documentation or