drm/amd: Fix hang on amdgpu unload by using pci_dev_is_disconnected()

drm/amd: Fix hang on amdgpu unload by using pci_dev_is_disconnected()

The commit 6a23e7b4332c ("drm/amd: Clean up kfd node on surprise
disconnect") introduced early KFD cleanup when drm_dev_is_unplugged()
returns true. However, this causes hangs during normal module unload
(rmmod amdgpu).

The issue occurs because drm_dev_unplug() is called in amdgpu_pci_remove()
for all removal scenarios, not just surprise disconnects. This was done
intentionally in commit 39934d3ed572 ("Revert "drm/amdgpu: TA unload
messages are not actually sent to psp when amdgpu is uninstalled"") to
fix IGT PCI software unplug test failures. As a result,
drm_dev_is_unplugged() returns true even during normal module unload,
triggering the early KFD cleanup inappropriately.

The correct check should distinguish between:
- Actual surprise disconnect (eGPU unplugged): pci_dev_is_disconnected()
  returns true
- Normal module unload (rmmod): pci_dev_is_disconnected() returns false

Replace drm_dev_is_unplugged() with pci_dev_is_disconnected() to ensure
the early cleanup only happens during true hardware disconnect events.

Cc: stable@vger.kernel.org
Reported-by: Cal Peake <cp@absolutedigital.net>
Closes: https://lore.kernel.org/all/b0c22deb-c0fa-3343-33cf-fd9a77d7db99@absolutedigital.net/
Fixes: 6a23e7b4332c ("drm/amd: Clean up kfd node on surprise disconnect")
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>