drm/amdgpu: seq64 memory unmap uses uninterruptible lock

To unmap and free seq64 memory when drm node close to free vm, if there
is signal accepted, then taking vm lock failed and leaking seq64 va
mapping, and then dmesg has error log "still active bo inside vm".

Change to use uninterruptible lock fix the mapping leaking and no dmesg
error log.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>