[rom_ctrl,doc] Remove dotted box from block diagram
[rom_ctrl,doc] Remove dotted box from block diagram

When we originally specced this module out, it looked like it might be
a good idea to implement the "scrambled ROM" with a primitive. As it
turns out, this was pretty simple and it's probably easier to just
inline it. Update the block diagram to match.

Signed-off-by: Rupert Swarbrick <290093e2ad2515ed2f14d749293c8cf8e02ca274@lowrisc.org>

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