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>

include/linux/ide.h

@@ -1327,6 +1327,8 @@ enum {
 	IDE_HFLAG_SERIALIZE		= (1 << 20),
 	/* host is DTC2278 */
 	IDE_HFLAG_DTC2278		= (1 << 21),
+	/* 4 devices on a single set of I/O ports */
+	IDE_HFLAG_4DRIVES		= (1 << 22),
 	/* host is TRM290 */
 	IDE_HFLAG_TRM290		= (1 << 23),
 	/* use 32-bit I/O ops */