at86rf230: use irq_get_trigger_type

This patch removes the platform data for the irq_type. We use instead
the irq_get_trigger_type function to get these flags which should
already configured by the interrupt controller.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>