ide-pmac: remove pmac_ide_do_setfeature() (take 2)

Use ide_config_drive_speed() instead of pmac_ide_do_setfeature() and remove
the latter, also  ide-iops.c::__ide_wait_stat() could be static again.

Since for IDE PMAC host driver IDE_CONTROL_REG is always true, device's
->quirk_list is always zero and ->ide_dma_host_{on,off} are nops than
the only changes in behavior are:

* if PIO mode is set then ->dma_off_queitly is called to disable DMA

* if setting transfer mode fails ide_dump_status() is called to dump status

v2:
* IDE PMAC controllers allow separate PIO and DMA timings and PPC userland
  depends on this fact, and calls "hdparm -p" without calling "hdparm -d".

  Therefore to compensate for DMA being disabled by ide_config_drive_speed()
  for PIO modes:

  - add IDE_HFLAG_SET_PIO_MODE_KEEP_DMA flag and set it in PMAC host driver

  - add handling of the new flag to ide-io.c::do_special()

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

include/linux/ide.h

@@ -1153,7 +1153,6 @@ extern void SELECT_MASK(ide_drive_t *, int);
 extern void QUIRK_LIST(ide_drive_t *);
 
 extern int drive_is_ready(ide_drive_t *);
-int __ide_wait_stat(ide_drive_t *, u8, u8, unsigned long);
 
 /*
  * taskfile io for disks for now...and builds request from ide_ioctl
@@ -1253,6 +1252,11 @@ enum {
 	IDE_HFLAG_ABUSE_FAST_DEVSEL	= (1 << 5),
 	/* use 100-102 and 200-202 PIO values to set DMA modes */
 	IDE_HFLAG_ABUSE_DMA_MODES	= (1 << 6),
+	/*
+	 * keep DMA setting when programming PIO mode, may be used only
+	 * for hosts which have separate PIO and DMA timings (ie. PMAC)
+	 */
+	IDE_HFLAG_SET_PIO_MODE_KEEP_DMA	= (1 << 7),
 };
 
 typedef struct ide_pci_device_s {