iflib: Avoid double counting in rxeof

iflib_rxeof() was counting everything twice. This was introduced when
pfil hooks were added to the iflib receive path. We want to count rx
packets/bytes before the pfil hooks are executed, so remove the counter
adjustments that are executed after.

PR: 253583
Reviewed by: gallatin, erj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28900

(cherry picked from commit b6999635b195e8c0dd5c08ac9ff268c92107cc66)