Danilo Krummrich

A refcount underflow issue has been resolved in the Linux kernel. The issue occurs when `nouveau bo ref()` is called on a `nouveau bo` without initializing it, leading to a refcount underflow. To fix this, the code now cleans up manually instead of calling `nouveau bo ref()` in the unwind path of `drm gem object init()`.

The issue is related to a memory leak in the `pci iounmap()` function. The `#ifdef ARCH HAS GENERIC IOPORT MAP` guard accidentally also guards `iounmap()`, resulting in MMIO mappings being leaked. To fix this, the guard needs to be moved so that `iounmap()` is called for MMIO mappings. This could potentially allow an attacker to cause a denial of service.