Revert "net/sched: act_api: move TCA_EXT_WARN_MSG to the correct hierarchy"

Revert "net/sched: act_api: move TCA_EXT_WARN_MSG to the correct hierarchy"

This reverts commit 923b2e30dc9cd05931da0f64e2e23d040865c035.

This is not a correct fix as TCA_EXT_WARN_MSG is not a hierarchy to
TCA_ACT_TAB. I didn't notice the TC actions use different enum when adding
TCA_EXT_WARN_MSG. To fix the difference I will add a new WARN enum in
TCA_ROOT_MAX as Jamal suggested.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>