Use mbedtls from Crypto SP in SMMGW

Crypto SP provides hash calculation and signature verification API-s
that will be used by the uefi service in SMMGW SP.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: I03e2862662734275221481784d82d8498c6f08af
diff --git a/protocols/service/smm_variable/parameters.h b/protocols/service/smm_variable/parameters.h
index 233f301..d8918b4 100644
--- a/protocols/service/smm_variable/parameters.h
+++ b/protocols/service/smm_variable/parameters.h
@@ -7,6 +7,8 @@
 #ifndef TS_SMM_VARIABLE_PARAMETERS_H
 #define TS_SMM_VARIABLE_PARAMETERS_H
 
+#include <stddef.h>
+
 #include "protocols/common/efi/efi_status.h"
 #include "protocols/common/efi/efi_types.h"