tests/tcg: fix missing return

This was picked up when clang built the test.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210512102051.12134-30-alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

tests/tcg/multiarch/system/memory.c

@@ -326,6 +326,7 @@ static bool do_unsigned_test(init_ufn fn)
         fn(i);
         ok = do_unsigned_reads(i);
     }
+    return ok;
 #else
     fn(0);
     return do_unsigned_reads(0);