ide: add IDE_HFLAG_BOOTABLE host flag

Add IDE_HFLAG_BOOTABLE host flag and IDE_HFLAG_OFF_BOARD define.  Convert
all host drivers using ide_pci_device_t to use IDE_HFLAG_{BOOTABLE,OFF_BOARD}
instead of d->bootable and then remove no longer needed d->bootable.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/siimage.c b/drivers/ide/pci/siimage.c
index 4c81083..5ff7968 100644
--- a/drivers/ide/pci/siimage.c
+++ b/drivers/ide/pci/siimage.c
@@ -920,7 +920,7 @@
 		.init_hwif	= init_hwif_siimage,	\
 		.fixup		= siimage_fixup,	\
 		.autodma	= AUTODMA,		\
-		.bootable	= ON_BOARD,		\
+		.host_flags	= IDE_HFLAG_BOOTABLE,	\
 		.pio_mask	= ATA_PIO4,		\
 	}