Add support for routing an IRQ from the normal ARM IRQ mechanism to the
FIQ input of the processor.

Note, also fix a bug where the init_FIQ() function has not been called
when CONFIG_FIQ is enabled.

Signed-off-by; Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>