KVM: arm64: nv: Add trap forwarding for HFGxTR_EL2

Implement the trap forwarding for traps described by HFGxTR_EL2,
reusing the Fine Grained Traps infrastructure previously implemented.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Jing Zhang <jingzhangos@google.com>
Link: https://lore.kernel.org/r/20230815183903.2735724-21-maz@kernel.org