drm/amdgpu: Replace tmp_adev with hive in amdgpu_pci_slot_reset

Checking hive is more readable.

The following smatch warning:
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:6820 amdgpu_pci_slot_reset()
warn: iterator used outside loop: 'tmp_adev'

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Ce Sun <cesun102@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>