The logic here is that the attestation is more than just the PCR0 value, and
multiple device firmware (such as EC, ME, etc.) needs to be included to validate
the system.
By the same logic, updates for the system firmware do not tell the whole story,
and confuse HSI as a specification. Remove them.
Firsly, that HSI isn't expected for embedded devices and then secondary how we
require SecureBoot to be available for HSI:1
At the moment we get a runtime failure if it is disabled. Making SB a part of
`HSI:1` makes this requiremnt explicit and prevents us getting `HSI:2!` if it
is not available.
