net/mlx5: check maximum modify actions number

net/mlx5: check maximum modify actions number

If the extensive metadata registers are supported,
it can be regarded inclusively that the extensive
metadata support is possible. E.g. metadata register
copy action, supporting 16 modify header actions,
reserving register across different steering domain
(FDB and NIC) and so on.

This patch handles the maximal amount of header modify
actions depending on discovered metadata registers
support.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>