The mlx5* driver(s) are built [*]/installed separate from the OFED stack thanks
to recent refactoring done in the linuxkpi(4) module.
Always install the manpages instead of conditionally installing them if
MK_OFED != no
* Further refactoring of sys/ofed and linuxkpi(4) is pending to fully divorce
mlx5* from ofed headers
MFC after: never
Requested by: hps