ASoC: WM8903: Free IRQ on device removal

Without this, request_irq on subsequent device initialization fails, and
the codec cannot be used.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>