net/mlx5: fix sample flow action on trusted device

net/mlx5: fix sample flow action on trusted device

A flow rule with sample action will be split into two sub flows,
and a tag action was added implicitly in the sample prefix sub flow,
the reserved metadata regC index was used for this tag action.

The reserved metadata regC was shared with metering action,
for ConnectX-5 trusted device (VF/SF), the reserved metadata regC was
invalid since PF only supported the legacy metering.

This patch adds the checking for the tag index and back to use the
application tag if a failure happened.

Fixes: a9b6ea45bed6 ("net/mlx5: fix tag ID conflict with sample action")
Cc: stable@dpdk.org
Signed-off-by: Jiawei Wang <jiaweiw@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>