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
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28900