habanalabs: remove releasing of user threads from device release

The device file is not in use when hl_device_release() is called,
and there aren't any user threads that use IOCTLs to wait for
interrupts. Therefore there is no need to release them at this point.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>