pcmcia: setup IRQ to be used by PCMCIA drivers at card insert

Setup the IRQ to be used by PCMCIA drivers already during the device
registration stage, making use of a new function pcmcia_setup_irq().
This will allow us to get rid of quite a lot of indirection in the
future.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>