ARM: PCI: add legacy IDE IRQ implementation

The IDE code used to specify the IDE IRQs for chipsets operating in
legacy mode.  This appears to no longer work, and this information must
be provided by the arch.  Do so.  This partially fixes CY82C693 (and
probably others) on Footbridge platforms.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>