habanalabs: correctly cast u64 to void*

Use the u64_to_user_ptr(x) kernel macro to correctly cast u64 to void*

Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Omer Shpigelman <oshpigelman@habana.ai>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Link: https://lore.kernel.org/r/20200601065648.8775-2-oded.gabbay@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>