mx6qsabresd has a AR8031 Gigabit PHY.

Add support for it.

Also increase CONFIG_SYS_MALLOC_LEN so that FEC buffer allocation does not fail.

Tested on 1Gbp and 100Mbps networks.

Suggested-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Kim Phillips <kim.phillips@freescale.com>