We are not aware of any out-of-tree consumers anymore
which would need KPI support for before Linux version 5.
Update the two in-tree consumers to use the new KPI.
This allows us to remove the extra version check and
will also give access to {lower,upper}_32_bits() unconditionally.
Sponsored-by: The FreeBSD Foundation
Reviewed-by: ..
MFC-after: 2 weeks
X-MFC: to 13 only
Differential Revision: