ide: make ide_hwif_t.ide_dma_host_on void (v2)

* since ide_hwif_t.ide_dma_host_on is called either when drive->using_dma == 1
  or when return value is discarded make it void, also drop "ide_" prefix
* make __ide_dma_host_on() void and drop "__" prefix

v2:
* while at it rename atiixp_ide_dma_host_on() to atiixp_dma_host_on()
  and sgiioc4_ide_dma_host_on() to sgiioc4_dma_host_on().
  [ Noticed by Sergei Shtylyov <sshtylyov@ru.mvista.com>. ]

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-iops.c

@@ -830,7 +830,7 @@ int ide_config_drive_speed (ide_drive_t *drive, u8 speed)
 
 #ifdef CONFIG_BLK_DEV_IDEDMA
 	if (speed >= XFER_SW_DMA_0)
-		hwif->ide_dma_host_on(drive);
+		hwif->dma_host_on(drive);
 	else if (hwif->ide_dma_check)	/* check if host supports DMA */
 		hwif->dma_off_quietly(drive);
 #endif