mmc: pxamci: remove irq from private context

This seems to be a left-over from times before the IRQ was handled by devm
functions. Remove it.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>