Revise crypto core register descriptions in RDL

[calebofearth]

Sha256/sha512/HMAC/ECC register descriptions should be updated in RDL (and ultimately in the generated HTML). There are two issues I see:

1. Address offsets for each reg are hardcoded in the text description. These are auto-generated when we create the HTML doc anyway, and subject to becoming outdated, so they shouldn't be hardcoded in the text.
2. Bit descriptions are redundantly provided in the register text description, but also in the subsequent section relative to each register field. As a result, there are some mismatches, and some of the text descriptions are missing certain bit fields. E.g. SHA256_CTRL has a text description that is missing all mention of WNTZ-related bits. All reg "field descriptions" should be updated and then individual field descriptions should be removed from the global register "description" field.