[M] Change in coreboot[main]: arch/arm64: Add EL1/EL2/EL3 support for arm64

[Nico Huber (Code Review)]

Attention is currently required from: Arthur Heymans, Christian Walter, David Milosevic, Julius Werner, Lean Sheng Tan, Maximilian Brune.

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74798?usp=email )

Change subject: arch/arm64: Add EL1/EL2/EL3 support for arm64
......................................................................

Patch Set 6:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/74798/comment/4eac0578_89a37ba7 :
PS5, Line 11: one boots into TF-A first and drops into EL2 for coreboot afterwards.
> Okay, so I have resolved all comments. […]

Just to make sure we're on the same page: We actually think it's wrong. We do it
anyway because $vendor. Chances to rectify things after the platform is upstream
are close to 0 because discussions with $vendor about it haven't even started yet.
Is that correct?

And to have it said: arguments that discussions will be too slow / too late
usually don't help when somebody forgot to start them a year ago.

If Julius agrees to the patch, I won't object. However, I would wait with merging
until there was an actual decision to accept Ampere support upstream (we don't
know yet what other obstacles exist and what other people think of a shimboot).