CVE-2026-46118 pseries/papr-hvpipe: Fix null ptr deref in papr_hvpipe_dev_create_handle()

In the Linux kernel, the following vulnerability has been resolved: pseries/papr-hvpipe: Fix null ptr deref in paprhvpipedevcreatehandle commit 6d3789d347a7 "papr-hvpipe: convert paprhvpipedevcreatehandle to FDPREPARE", changed the create handle to FDPREPARE, but it caused kernel null-ptr-deref...