microblaze: Remove NO_IRQ from architecture

NO_IRQ shouldn't be used by any driver. All Microblaze
drivers are fixed that's why NO_IRQ can be removed.

Also fix pci-common.c which has references to NO_IRQ removed.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Reviewed-by: Ryan Mallon <rmallon@gmail.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>