Follow the pattern introduced with vcpu_set_hcr(), and introduce
vcpu_set_ich_hcr(), which configures the GICv3 traps at the same
point.

This will allow future changes to introduce trap configuration on
a per-VM basis.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240827152517.3909653-2-maz@kernel.orgSigned-off-by: Marc Zyngier <maz@kernel.org>