drm/amdkfd: Cleanup IO links during KFD device removal

Currently, the IO-links to the device being removed from topology,
are not cleared. As a result, there would be dangling links left in
the KFD topology. This patch aims to fix the following:
1. Cleanup all IO links to the device being removed.
2. Ensure that node numbering in sysfs and nodes proximity domain
   values are consistent after the device is removed:
   a. Adding a device and removing a GPU device are made mutually
      exclusive.
   b. The global proximity domain counter is no longer required to be
      an atomic counter. A normal 32-bit counter can be used instead.
3. Update generation_count to let user-mode know that topology has
   changed due to device removal.

CC: Shuotao Xu <shuotaoxu@microsoft.com>
Reviewed-by: Shuotao Xu <shuotaoxu@microsoft.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>