AT91: Remove fixed mapping for AT91RM9200 ethernet

The AT91RM9200 Ethernet controller still has a fixed IO mapping.
So:
* Remove the fixed IO mapping and AT91_VA_BASE_EMAC definition.
* Pass the physical base-address via platform-resources to the driver.
* Convert at91_ether.c driver to perform an ioremap().
* Ethernet PHY detection needs to be performed during the driver
initialization process, it can no longer be done first.

Signed-off-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>