Revert "genirq: Restrict effective affinity to interrupts actually using it"

This reverts commit 74def747.

The change to the helper function is only correct for the /proc/irq/
readout usage, but breaks the existing x86 usage of that function.

Reported-by: Yanko Kaneti <yaneti@declera.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>