inline most of the considered lost condensation.

This is a small cleanup to consolidate the considered lost reduction and marking to an
inline function. There are two places where we are using hookery in SACK processing where
we can't use it. All other places we move to the function. This code in theory changes nothing
and just makes things a bit more readable and consistent.

Reviewed by:tuexen
Differential Revision: https://reviews.freebsd.org/D53021