vxlan: Handle stats using NETDEV_PCPU_STAT_DSTATS.

VXLAN uses the TSTATS infrastructure (dev_sw_netstats_*()) for RX and
TX packet counters. It also uses the device core stats
(dev_core_stats_*()) for RX and TX drops.

Let's consolidate that using the DSTATS infrastructure, which can
handle both packet counters and packet drops. Statistics that don't
fit DSTATS are still updated atomically with DEV_STATS_INC().

While there, convert the "len" variable of vxlan_encap_bypass() to
unsigned int, to respect the types of skb->len and
dev_dstats_[rt]x_add().

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Link: https://patch.msgid.link/145558b184b3cda77911ca5682b6eb83c3ffed8e.1733313925.git.gnault@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>