amdkfd: destroy kfd secondary contexts through fd close

amdkfd: destroy kfd secondary contexts through fd close

Life cycle of a KFD secondary context(kfd_process) is tied
to the opened file. Therefore this commit destroy a kfd
secondary context when close the fd it belonging to.

This commit extracts the code removing the kfd_process
from the kfd_process_table to a separate function and
call it in kfd_process_notifier_release_internal unconditionally.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>