PCMCIA: stop duplicating pci_irq in soc_pcmcia_socket

skt->irq is a mere duplication of pcmcia_socket's pci_irq member.
Get rid of it.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>