init: allow init to be called multiple times

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/maa.h

@@ -50,6 +50,7 @@ typedef enum {
     MAA_ERROR_NO_DATA_AVAILABLE              =  9, /**< No data available */
     MAA_ERROR_INVALID_PLATFORM               = 10, /**< Platform not recognised */
     MAA_ERROR_PLATFORM_NOT_INITIALISED       = 11, /**< Board information not initialised */
+    MAA_ERROR_PLATFORM_ALREADY_INITIALISED   = 12, /**< Board is already initialised
 
     MAA_ERROR_UNSPECIFIED                    = 99 /**< Unknown Error */
 } maa_result_t;