Earl Grey OTP scrambling

[jwnrt]

Darjeeling supports OTP scrambling; we need to backport that to Earl Grey.

Until then the following properties are disabled under ot-otp-eg:

• digest_const
• digest_iv
• sram_const
• sram_iv

[jwnrt]

I've also noticed that cfggen.py is no longer generating the scrmbl_key constant. Maybe this moved to another SV file with the recent OTP generation changes.

EDIT: fixed by #124