doc: update mlx4 usage and dependencies
doc: update mlx4 usage and dependencies

- libmlx4 and libibverbs dependencies distributed with Mellanox OFED are now
  also available on DPDK.org to make installation easier.
- Document Mellanox OFED and firmware versions to use.
- Add links to Mellanox and its community websites.
- Add kernel modules parameters section.

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

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk