gianfar: Include missing headers for ARM builds

Include linux/of_address.h for of_iomap() and linux/of_irq.h
for irq_of_parse_and_map().

This wasn't an issue for PPC, because these were implicitly
included from asm/prom.h (via linux/of.h) for PPC builds only.
ARM builds need these includes explicitly.

Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>