icside: use ec->dma directly

* hwif->hwif_data contains pointer to struct expansion_card so use ec->dma
  directly instead of caching it in hwif->hw.dma.

* Remove no longer needed hw_regs_t.dma and NO_DMA define.

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