KVM: arm64: Free hypervisor allocations if vector slot init fails

Teardown hypervisor mode if vector slot setup fails in order to avoid
leaking any allocations done by init_hyp_mode().

Fixes: b881cdce ("KVM: arm64: Allocate hyp vectors statically")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221130230934.1014142-18-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>