habanalabs: use NULL for eventfd

eventfd is pointer. As such, it should be initialized to NULL, not to 0.

In addition, no need to initialize it after creation because the
entire structure is zeroed-out. Also, no need to initialize it before
release because the entire structure is freed.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>