Remove Yotta support from the docs, tests and build scripts

Yotta is no longer supported by Mbed TLS, so has been removed. Specifically, the
following changes have been made:
 * references to yotta have been removed from the main readme and build
   instructions
 * the yotta module directory and build script has been removed
 * yotta has been removed from test scripts such as all.sh and check-names.sh
 * yotta has been removed from other files that that referenced it such as the
   doxyfile and the bn_mul.h header
 * yotta specific configurations and references have been removed from config.h
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 81438c5..91d0cdb 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -3130,23 +3130,12 @@
 
 /* \} name SECTION: Customisation configuration options */
 
-/* Target and application specific configurations */
-//#define YOTTA_CFG_MBEDTLS_TARGET_CONFIG_FILE "target_config.h"
-
-#if defined(TARGET_LIKE_MBED) && defined(YOTTA_CFG_MBEDTLS_TARGET_CONFIG_FILE)
-#include YOTTA_CFG_MBEDTLS_TARGET_CONFIG_FILE
-#endif
-
-/*
+/* Target and application specific configurations
+ *
  * Allow user to override any previous default.
  *
- * Use two macro names for that, as:
- * - with yotta the prefix YOTTA_CFG_ is forced
- * - without yotta is looks weird to have a YOTTA prefix.
  */
-#if defined(YOTTA_CFG_MBEDTLS_USER_CONFIG_FILE)
-#include YOTTA_CFG_MBEDTLS_USER_CONFIG_FILE
-#elif defined(MBEDTLS_USER_CONFIG_FILE)
+#if defined(MBEDTLS_USER_CONFIG_FILE)
 #include MBEDTLS_USER_CONFIG_FILE
 #endif