mlx5: fix build with GCC < 4.6
mlx5: fix build with GCC < 4.6

Seen with GCC < 4.6:

 error: unknown field ‘tcp_udp’ specified in initializer
 error: extra brace group at end of initializer

Static initialization of anonymous structs/unions is a C11 feature
properly supported only since GCC 4.6.

Work around compilation errors with older versions by expanding
struct ibv_exp_flow_spec into struct hash_rxq_init.

Signed-off-by: Yaacov Hazan <b9b45a5a3790ec570f214ff47368ef7b63d38fb3@mellanox.com>
Signed-off-by: Adrien Mazarguil <9d39ea493ca46c560334f650ac5d4b5ffbcb5cf0@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk