KVM: arm64: Add early_param to control WFx trapping

KVM: arm64: Add early_param to control WFx trapping

Add an early_params to control WFI and WFE trapping. This is to
control the degree guests can wait for interrupts on their own without
being trapped by KVM. Options for each param are trap and notrap. trap
enables the trap. notrap disables the trap. Note that when enabled,
traps are allowed but not guaranteed by the CPU architecture. Absent
an explicitly set policy, default to current behavior: disabling the
trap if only a single task is running and enabling otherwise.

Signed-off-by: Colton Lewis <coltonlewis@google.com>
Reviewed-by: Jing Zhang <jingzhangos@google.com>
Link: https://lore.kernel.org/r/20240523174056.1565133-1-coltonlewis@google.com
[ oliver: rework kvm_vcpu_should_clear_tw*() for readability ]
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>