When check_kvm_guest() succeeds in looking up a /hypervisor OF node, it
returns without performing a matching put for the lookup, leaving the
node's reference count elevated.
Add the necessary call to of_node_put(), rearranging the code slightly to
avoid repetition or goto.
Signed-off-by: Nathan Lynch <redacted>
Fixes: 107c55005fbd ("powerpc/pseries: Add KVM guest doorbell restrictions")