KVM: arm64: Prevent guests from enabling HA/HD on Ampere1

An erratum in the HAFDBS implementation in AmpereOne was addressed by
clearing the feature in the ID register, with the expectation that
software would not attempt to use the corresponding controls in TCR_EL1.
The architecture, on the other hand, takes a much more pedantic stance
on the subject, requiring the TCR bits behave as RES0.

Take an extremely conservative stance on the issue and leverage the
precise write trap afforded by FGT. Handle guest writes by clearing HA
and HD before writing the intended value to the EL1 register alias.

Link: https://lore.kernel.org/r/20230609220104.1836988-4-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>