[ide] small compile fix to ide.c with !CONFIG_PCI

Small patch to fix following warning with CONFIG_IDE && !CONFIG_PCI:

  CC	drivers/ide/ide.o
drivers/ide/ide.c: In function 'ide_system_bus_speed':
drivers/ide/ide.c:338: warning: unused variable 'pci_default'

I decided to save some bytes by #ifdef:ing the struct in question.
CC:ing Hanna because she did the change (and just to say hi ;-).
Signed-off-by: Mika Kukkonen <mikukkon@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide.c

@@ -335,10 +335,14 @@ static void __init init_ide_data (void)
 
 static int ide_system_bus_speed(void)
 {
+#ifdef CONFIG_PCI
 	static struct pci_device_id pci_default[] = {
 		{ PCI_DEVICE(PCI_ANY_ID, PCI_ANY_ID) },
 		{ }
 	};
+#else
+#define pci_default 0
+#endif /* CONFIG_PCI */
 
 	if (!system_bus_speed) {
 		if (idebus_parameter) {