ARM: 7309/1: realview: fix unconnected interrupts on EB11MP

Since commit 2eac58d (ARM: amba: make use of -1 IRQs warn), we're
able to detect the use of value -1 to indicate the lack of interrupt
line.

The RealView EB, when used with the 11MPCore tile, has a number of
devices without interrupts, and uses the value -1 to indicate this.

Change that value to 0 to conform to the new behaviour.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>