CVE-2026-98179: drm/amdgpu: fix rmmio iounmap skipped on device removal

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

drm/amdgpu: fix rmmio iounmap skipped on device removal

amdgpupciremove() calls drmdevunplug() before finisw(), so drmdeventer() is already false there and the iounmap() guarded by it is skipped. This .remove path runs on both hot-unplug and plain rmmod, so the register BAR ioremap mapping leaks one instance per unload.

Unmap rmmio unconditionally (guard only on non-NULL) and drop the now unused idx.

(cherry picked from commit dd6f86a97260e5207d3329ad03aa89fdad61b1e6)