All the LinuxKPI base wireless drivers had the same texts in each
man page only with the driver name changed.
Try to migrate most of the common texts into linuxkpi_wlan.4 leaving
only a minimalistic paragraph pointing there.
This also moves descriptive texts out of the SYNOPSIS section [1],
which has now become entirely removed for the drivers.
Add .Lk to the bug hierarchies we are trying to keep for all of the
drivers, as we did for iwlwifi.4 before.
iwlwififw.4 is now orphaned and removed (as indicated before given
automatic generation of the file is no longer possible or hightly
inaccurate).
Suggested by: ziaee (in D58479)
MFC after: 3 days