Fix use of sizeof without brackets

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index 85c00eb..7d81608 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -284,7 +284,7 @@
     }
     TEST_EQUAL(test_offset_idx, expected_idx);
 
-    /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT).
+    /* Call update with too much data (sizeof(entropy) > MAX(_SEED)_INPUT).
      * Make sure it's detected as an error and doesn't cause memory
      * corruption. */
     TEST_ASSERT(mbedtls_ctr_drbg_update(