Fix Earlgrey regression in ot_entropy_src

[loiclefort]

REV register was removed from entropy_src in OpenTitan commit e7675d760235cbcfa327be948196b6418d10ff54.

[AlexJones0]

Thanks, this LGTM. Unfortunately, the register will be present in earlgrey_1.0.0.

I have an upcoming PR to switch the Earlgrey definition on ot-earlgrey-9.2.0 to emulate Earlgrey 1.0.0, so I'll rebase on top of this change and probably separate the entropy source into an ot_entropy_src_eg and ot_entropy_src_dj

[AlexJones0]

Actually, I didn't realise that Darjeeling didn't have an entropy_src.

I think in that case given the intention to move to emulating earlgrey_1.0.0, it may not make sense to make this change to then immediately revert it?

[loiclefort]

Actually, I didn't realise that Darjeeling didn't have an entropy_src.

The "old" darjeeling from the initial opentitan-integrated work did not have an entropy_src but is was added back.

[AlexJones0]

The "old" darjeeling from the initial opentitan-integrated work did not have an entropy_src but is was added back.

Ah, I see. I didn't realize that this was recently changed. Sorry for the confusion.

In that case, yes, I think it is best to merge this and then separate EG 1.0.0 and DJ definitions in my follow-up PR.