net/sched: simplify tcf_pedit_act

[ Upstream commit 95b06938 ]

Remove the check for a negative number of keys as
this cannot ever happen

Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: 6c02568f ("net/sched: act_pedit: Parse L3 Header for L4 offset")
Signed-off-by: Sasha Levin <sashal@kernel.org>