icside: use ide_tune_dma()

* Add "good DMA drives" hack for icside to ide-dma.c::ide_find_dma_mode()
  (in the long-term it should be either removed or generalized for all hosts).

* Use ide_tune_dma() in icside.c::icside_dma_check().

  This results in the following changes in behavior:
  - pre-EIDE SWDMA modes are now also respected
  - drive->autodma is checked instead of hwif->autodma
    (doesn't really matter as icside sets both to "1")

* Make ide-dma.c::__ide_dma_good_drive() static and drop "__" prefix.

Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>