net: tun: split run_ebpf_filter() and pskb_trim() into different "if statement"

net: tun: split run_ebpf_filter() and pskb_trim() into different "if statement"

BugLink: https://bugs.launchpad.net/bugs/1988479
[ Upstream commit 45a15d89fbcd280571eba8e5ca309e14ba6afa8f ]

No functional change.

Just to split the if statement into different conditions to use
kfree_skb_reason() to trace the reason later.

Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>