Replace MBEDTLS_MD_CAN_SHA384 with PSA_WANT_ALG_SHA_384

Signed-off-by: Elena Uziunaite <elena.uziunaite@arm.com>
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index 2772cac..fd6cba0 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -44,7 +44,7 @@
 #define COOKIE_MD           MBEDTLS_MD_SHA256
 #define COOKIE_MD_OUTLEN    32
 #define COOKIE_HMAC_LEN     28
-#elif defined(MBEDTLS_MD_CAN_SHA384)
+#elif defined(PSA_WANT_ALG_SHA_384)
 #define COOKIE_MD           MBEDTLS_MD_SHA384
 #define COOKIE_MD_OUTLEN    48
 #define COOKIE_HMAC_LEN     28