Merge branch 'ipv4-prepare-core-ipv4-files-to-future-flowi4_tos-conversion'

Guillaume Nault says:

====================
ipv4: Prepare core ipv4 files to future .flowi4_tos conversion.

Continue preparing users of ->flowi4_tos (struct flowi4) to the future
conversion of this field (from __u8 to dscp_t). The objective is to
have type annotation to properly separate DSCP bits from ECN ones. This
way we'll ensure that ECN doesn't interfere with DSCP and avoid
regressions where it break routing descisions (fib rules in particular).

This series concentrates on some easy IPv4 conversions where
->flowi4_tos is set directly from an IPv4 header, so we can get the
DSCP value using the ip4h_dscp() helper function.
====================

Link: https://patch.msgid.link/cover.1729530028.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>