CVE-2026-72328: accel/amdxdna: Fix potential amdxdna_umap lifetime race

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

accel/amdxdna: Fix potential amdxdnaumap lifetime race

amdxdnaumaprelease() calls the blocking mmuintervalnotifierremove() before removing the object from abo->mem.umaplist. If aie2populaterange() runs concurrently, it may obtain a reference to an amdxdnaumap that is being released, leading to a potential use-after-free.

Use krefgetunlesszero() in aie2populaterange() when acquiring a reference. If the reference count has already dropped to zero, release is in progress and the entry is skipped.