ide: add missing validity checks for identify words 62 and 63

Check validity of identify words 62 and 63 before using them in
ide_get_mode_mask().
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-dma.c

@@ -731,10 +731,12 @@ static unsigned int ide_get_mode_mask(ide_drive_t *drive, u8 base)
 			mask &= 0x07;
 		break;
 	case XFER_MW_DMA_0:
-		mask = id->dma_mword & hwif->mwdma_mask;
+		if (id->field_valid & 2)
+			mask = id->dma_mword & hwif->mwdma_mask;
 		break;
 	case XFER_SW_DMA_0:
-		mask = id->dma_1word & hwif->swdma_mask;
+		if (id->field_valid & 2)
+			mask = id->dma_1word & hwif->swdma_mask;
 		break;
 	default:
 		BUG();