KVM: arm64: Disable fields that KVM doesn't know how to handle in ID_AA64PFR1_EL1

KVM: arm64: Disable fields that KVM doesn't know how to handle in ID_AA64PFR1_EL1

For some of the fields in the ID_AA64PFR1_EL1 register, KVM doesn't know
how to handle them right now. So explicitly disable them in the register
accessor, then those fields value will be masked to 0 even if on the
hardware the field value is 1. This is safe because from a UAPI point of
view that read_sanitised_ftr_reg() doesn't yet return a nonzero value
for any of those fields.

This will benifit the migration if the host and VM have different values
when restoring a VM.

Those fields include RNDR_trap, NMI, MTE_frac, GCS, THE, MTEX, DF2, PFAR.

Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
Link: https://lore.kernel.org/r/20240723072004.1470688-2-shahuang@redhat.com
Signed-off-by: Marc Zyngier <maz@kernel.org>