mult_to_ibv_rate(3) on Linux

The text e8c6d1686e3b, as Arch Linux 2026-11-01 shipped it. The page shows this text now.

convert IB rate enumeration to multiplier of 2.5 Gbit/sec mult_to_ibv_rate - convert multiplier of 2.5 Gbit/sec to an IB rate enumeration