Simply pass the ioctl on to the normal handler. If the ioctl
helper macros are used correctly this should be safe as they
will handle the packing/unpacking of the data encoded in the
ioctl command. And actually, if the caller does not use the
IO* macros at all, and just passes small values, it will probably
be OK as well. We only get in to trouble if they try and use
the upper 32-bits. Endianness is not really a concern here, we
we are pretty much assumed they user and kernel will match.