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/alim15x3.c b/drivers/ide/pci/alim15x3.c
index 6f8ebc9..b6b44e9 100644
--- a/drivers/ide/pci/alim15x3.c
+++ b/drivers/ide/pci/alim15x3.c
@@ -777,7 +777,7 @@
 	.init_hwif	= init_hwif_ali15x3,
 	.init_dma	= init_dma_ali15x3,
 	.autodma	= AUTODMA,
-	.bootable	= ON_BOARD,
+	.host_flags	= IDE_HFLAG_BOOTABLE,
 	.pio_mask	= ATA_PIO5,
 };