genirq/msi: Drop artificial PCI dependency

The generic MSI layer doesn't have any PCI ties anymore, and the
build hack should have been removed some time ago.

Fixes: d9109698

 ("genirq: Introduce msi_domain_alloc/free_irqs()")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: http://lkml.kernel.org/r/1479806476-20801-1-git-send-email-marc.zyngier@arm.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>