smc911x: Add IRQ polarity configuration

Platforms like ARM Ltd's RealView require the IRQ polarity bit to be set
for the SMC9118 chip. This patch allows the dynamic configuration via
the smc911x_platdata structure.

This patch also changes the smc91x_platdata structure name to the
correct smc911x_platdata in the smc911x_drv_probe() function.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>