No need to trigger eviction as the memory mapping will not be used
anymore.

All pt/pd bos share same resv, hence the same shared eviction fence.
Everytime page table is freed, the fence will be signled and that cuases
kfd unexcepted evictions.

v2: squash in 32 bit fix

CC: Christian König <christian.koenig@amd.com>
CC: Felix Kuehling <felix.kuehling@amd.com>
CC: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>