net/mlx5: reorganize flow API structure

net/mlx5: reorganize flow API structure

Currently, the rte flow structure is not fully aligned and has some
bits wasted. The members can be optimized and reorganized to save
memory.

1. The drv_type uses only limited bits, change the type to 2 bits what
it needs.

2. Align the hairpin_flow_id, drv_type, fdir, copy_applied to 32 bits.
As hairpin never uses the full 32 bits.

3. __rte_packed helps tight up the structure memory layout.

The optimization totally helps save 14 bytes for the structure.

Signed-off-by: Suanming Mou <suanmingm@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>