fixup! New function mbedtls_rsa_get_bitlen

In some configurations (like config-mini-tls1_1.h), size is unused. This
leads to failures when building with CMake Asan, because that build
doesn't use "-Wno-unused-value".

Fixes: e01822299624 ("New function mbedtls_rsa_get_bitlen")
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index a1d9b0b..916b3c5 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -16,6 +16,7 @@
 static int pk_genkey( mbedtls_pk_context *pk, int size )
 {
     ((void) pk);
+    ((void) size);
 
 #if defined(MBEDTLS_RSA_C) && defined(MBEDTLS_GENPRIME)
     if( mbedtls_pk_get_type( pk ) == MBEDTLS_PK_RSA )