pcmcia: irq probe can be done without risking an IRQ storm

Nowdays you can ask for an IRQ to be allocated but not enabled, when PCMCIA
was written this was not true and this feature is thus not used

[linux@dominikbrodowski.net: add comment and ifdef to avoid compilation
 breakage at least on alpha]
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>