irdma(4): remove artificial completion generator

Removing artificial completion generator as there had been no indication
of the code being required for E810 cards. Further more it was found
that the code may have unpleasant side effects on user experience when
using ucmatose tool.

Signed-off-by: Bartosz Sobczak <bartosz.sobczak@intel.com>
Signed-off-by: Eric Joyner <erj@FreeBSD.org>

Reviewed by: erj@
MFC after: 1 day
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D41593