ARM: 7342/2: sa1100: prepare for sparse irq conversion

In preparation to convert SA1100 to sparse irq, set .nr_irqs for each machine
and explicitly include mach/irqs.h as needed.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>