ARM: Davinci DM355: Enabling DM9000 on DM355 EVM

Due to recent changes to the NET support on U-boot, DM9000
is no longer detected on the DM355 EVM.
This minor update enables DM9000 on the DM355 EVM.
Tested on the DM355 EVM

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>