[PARISC] Define pci_get_legacy_ide_irq

We can compile at least one IDE driver that refers to this.  We can't
use the asm-generic file because we have our own definitions of
pcibios_resource_to_bus etc.

Signed-off-by: Matthew Wilcox <willy@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>