net: davinci_emac: simplify the OF parser code

This patch cleans up the OF parser code, removes unnecessary checks
on of_property_read_*() and guards davinci_emac_of_match table with
CONFIG_OF.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>