[Doc] Add STSAFE-A Echo service dox file

doc/resources/dox_files/Services/stsafe_echo.dox

@@ -0,0 +1,52 @@
+\b Description
+This service format the STSAFE-A echo command/responces and call the MW core to perform frame exchange between host and target STSAFE-A device.
+Following diagram illustrates the interactions performed between the Host and the target STSE device during the service execution
+\n\n
+
+@startuml
+    'Define participant (define order = display order left to right)
+    participant "HOST" as HOST
+    participant "STSAFE-Axxx" as STSAFE
+
+    activate HOST $STSE_ACTIVITY
+    group stsafe_echo
+
+        rnote over HOST
+            Create command frame
+        end note
+
+        rnote over HOST
+            Create response frame
+        end note
+
+        HOST -> STSE : Echo ( Echo payload )
+        Activate STSAFE
+        return ( Echo payload )
+
+    end
+    deactivate HOST
+@enduml
+
+\n\n \b Use-case \b example
+\n The following applicative code snippet illustrates how to use this service in main application.
+\n\n
+
+\code{.c}
+
+    stse_ReturnCode_t ret;
+    PLAT_UI8 message[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
+    PLAT_UI8 echoed_message[] = {0};
+    PLAT_UI8 message_size = 8;
+
+    ret = stsafea_echo(pSTSE, message, echoed_message, message_size);
+
+	if(ret != STSE_OK )
+	{
+		/* Handle Error */
+	}
+
+\endcode
+
+\sa stsafe_init
+
+<div style="page-break-after: always;"></div>

services/stsafea/stsafea_echo.h

@@ -40,6 +40,7 @@
  * \param[in]	echoed_message		Message buffer to receive the echo response
  * \param[in]	message_size		Size of the echo message
  * \return \ref STSE_OK on success ; \ref stse_ReturnCode_t error code otherwise
+ * \details 	\include{doc} stse_data_storage_get_total_partition_count.dox
  */
 stse_ReturnCode_t stsafea_echo(
     stse_Handler_t *pSTSE,