IB/hfi1: Remove write(), use ioctl() for user cmds

Remove the write() handler for user space commands now that ioctl
handling is available. User apps will need to change to use ioctl from
this point forward.

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>