Fix suboptimal use of ASSER_ALLOC()

Passing a length of 0 to it is perfectly acceptable, the macro was designed to
handle it correctly.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 602dc36..5f301b5 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -4103,7 +4103,7 @@
         test_set_step( max_in_len * 10000 );
 
         /* Use allocated in buffer to catch overreads */
-        ASSERT_ALLOC( data, max_in_len != 0 ? max_in_len : 1 );
+        ASSERT_ALLOC( data, max_in_len );
 
         min_in_len = max_in_len > 255 ? max_in_len - 255 : 0;
         for( in_len = min_in_len; in_len <= max_in_len; in_len++ )