Merge pull request #958 from antonio-nino-diaz-arm/an/mbedtls-heap-size

mbedtls: Define optimized mbed TLS heap size

drivers/auth/mbedtls/mbedtls_common.c

@@ -16,7 +16,7 @@
 #if (TF_MBEDTLS_KEY_ALG_ID == TF_MBEDTLS_ECDSA)
 #define MBEDTLS_HEAP_SIZE		(14*1024)
 #elif (TF_MBEDTLS_KEY_ALG_ID == TF_MBEDTLS_RSA)
-#define MBEDTLS_HEAP_SIZE		(8*1024)
+#define MBEDTLS_HEAP_SIZE		(6*1024)
 #endif
 static unsigned char heap[MBEDTLS_HEAP_SIZE];