svwks: small cleanup

* remove redundant svwks_ide_dma_end() [ __ide_dma_end() is used by default ]
* remove init_dma_svwks() so the default ide_setup_dma() function is used
  [ init_setup_csb6() takes care of not initializing disabled channels ]

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