ARM: davinci: board-dm355-evm: fix broken networking

Since commit 09f3756b ("dm9000: Return an ERR_PTR() in all
error conditions of dm9000_parse_dt()"), passing either non-NULL
platform data or device-tree for dm9000 driver to probe is
mandatory.

DM335 board was using none, so networking failed to initialize.
Fix it by passing non-NULL (but empty) platform data.

Fixes: 09f3756b ("dm9000: Return an ERR_PTR() in all error conditions of dm9000_parse_dt()")
Signed-off-by: Sekhar Nori <nsekhar@ti.com>