ide: add device flags

Add 'unsigned long dev_flags' to ide_drive_t and convert bitfields
to IDE_DFLAG_* flags.

While at it:
- IDE_DFLAG_ADDRESSING -> IDE_DFLAG_LBA48
- fixup some comments
- remove needless g->flags zeroing from ide*_probe()

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/it821x.c b/drivers/ide/pci/it821x.c
index 46edd08..b761015 100644
--- a/drivers/ide/pci/it821x.c
+++ b/drivers/ide/pci/it821x.c
@@ -454,7 +454,7 @@
 		 *	IRQ mask as we may well be in PIO (eg rev 0x10)
 		 *	for now and we know unmasking is safe on this chipset.
 		 */
-		drive->unmask = 1;
+		drive->dev_flags |= IDE_DFLAG_UNMASK;
 	} else {
 	/*
 	 *	Perform fixups on smart mode. We need to "lose" some