Merge branch 'skip_sw-skip_hw-validation'

Davide Caratti says:

====================
add missing validation of 'skip_hw/skip_sw'

ensure that all classifiers currently supporting HW offload
validate the 'flags' parameter provided by user:

- patch 1/2 fixes cls_matchall
- patch 2/2 fixes cls_flower
====================

Signed-off-by: David S. Miller <davem@davemloft.net>