CVE-2024-26691 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.