Ensure fid() calls make_id() for consistency; tests/simple/dff_init.v fails

Mark dff_init.v as expected to fail since it uses "initial value".

tests/simple/xfirrtl

@@ -1,6 +1,7 @@
 # This file contains the names of verilog files to exclude from verilog to FIRRTL regression tests due to known failures.
 arraycells.v	inst id[0] of
 dff_different_styles.v
+dff_init.v	Initial value not supported
 generate.v	combinational loop
 hierdefparam.v	inst id[0] of
 i2c_master_tests.v   $adff