Fix compiling issue when CFG_TEE_TA_LOG_LEVEL=0

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Pascal Brand <pascal.brand@st.com>
diff --git a/ta/os_test/os_test.c b/ta/os_test/os_test.c
index 335d3c9..30471d0 100644
--- a/ta/os_test/os_test.c
+++ b/ta/os_test/os_test.c
@@ -51,7 +51,7 @@
 };
 
 static TEE_Result check_returned_prop(
-		int line, char *prop_name,
+		int line __maybe_unused, char *prop_name __maybe_unused,
 		TEE_Result return_res, TEE_Result expected_res,
 		uint32_t return_len, uint32_t expected_len)
 {