drm/amdgpu: Skip KFD mapping clear before initialization

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

drm/amdgpu: Skip KFD mapping clear before initialization

amdgpu_amdkfd_clear_kfd_mapping() assumes that a non-NULL kfd_dev
has a fully populated node array. This is not true when KFD device
initialization fails after probe.

For example, kgd2kfd_device_init() sets num_nodes before checking
PCIe atomics support. On Polaris systems without the required atomics,
it returns before allocating nodes[0], but the kfd_dev remains attached
to the amdgpu device. A later GPU reset then dereferences nodes[0]->id.

Require the authoritative KFD initialization flag before walking the
node array, matching the existing KFD reset and teardown paths.

(cherry picked from commit 4ac1835823c47903fbb278bbf474773c46f59edc)