ide: add IDE_HFLAG_4DRIVES host flag

Add IDE_HFLAG_4DRIVES host flag and use it instead of ide_4drives
chipset type in ide_init_port().

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-probe.c b/drivers/ide/ide-probe.c
index 62270f4..335322f 100644
--- a/drivers/ide/ide-probe.c
+++ b/drivers/ide/ide-probe.c
@@ -1381,8 +1381,8 @@
 		if (ide_probe_port(hwif) == 0)
 			hwif->present = 1;
 
-		if (hwif->chipset != ide_4drives || !hwif->mate ||
-		    !hwif->mate->present) {
+		if ((hwif->host_flags & IDE_HFLAG_4DRIVES) == 0 ||
+		    hwif->mate == NULL || hwif->mate->present == 0) {
 			if (ide_register_port(hwif)) {
 				ide_disable_port(hwif);
 				continue;