Instead of not installing the missing man page - use the one from the previous
version.
Changes include:
- Revert all the MANPAGEEXISTS-related changes from net/intel-{ixl,ix}-kmod
- Allow slave ports of net/intel-ixl-kmod to set their own MASTER_SITES
- Add previous version of intel-ix-kmod to it's DISTFILES
- Add pre-install target to intel-ixl-kmod to place the man page where
do-install expects to find it
6d184086ef