KVM: arm64: Fix circular locking dependency

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Fix circular locking dependency

The rule inside kvm enforces that the vcpu->mutex is taken *inside*

kvm->lock. The rule is violated by the pkvm_create_hyp_vm() which acquires

the kvm->lock while already holding the vcpu->mutex lock from

kvm_vcpu_ioctl(). Avoid the circular locking dependency altogether by

protecting the hyp vm handle with the config_lock, much like we already

do for other forms of VM-scoped data.