Simplify the test and description

Previously the check was convoluted. This has been simplified
and given a more appropriate suggestion as per gilles suggestion

Signed-off-by: Joe Subbiani <joe.subbiani@arm.com>
diff --git a/tests/suites/test_suite_psa_crypto_metadata.function b/tests/suites/test_suite_psa_crypto_metadata.function
index f2dcfca..1db3ca6 100644
--- a/tests/suites/test_suite_psa_crypto_metadata.function
+++ b/tests/suites/test_suite_psa_crypto_metadata.function
@@ -630,27 +630,9 @@
                 PSA_KEY_TYPE_CATEGORY_SYMMETRIC );
     TEST_EQUAL( PSA_BLOCK_CIPHER_BLOCK_LENGTH( type ), block_size );
 
-    /* PSA_ROUND_UP_TO_MULTIPLE(block_size, length) in crypto_sizes.h
-     * Requires block sizes to be a power of 2.
-     * The following creates a bit and shifts along until it finds a
-     * match or a mismatch.
-     */
-    int check = 0;
-
-    for (size_t index = 1; index > 0; index = index << 1)
-    {
-        if (index == block_size)
-        {
-            check = 0;
-            break;
-        }
-        if (index > block_size)
-        {
-            check = 1;
-            break;
-        }
-    }
-    TEST_EQUAL( check, 0);
+    /* Check that the block size is a power of 2. This is required, at least, 
+    for PSA_ROUND_UP_TO_MULTIPLE(block_size, length) in crypto_sizes.h. */
+    TEST_ASSERT( ( ( block_size - 1 ) & block_size ) == 0 );
 }
 /* END_CASE */