ide: use ide_destroy_dmatable() instead of pci_unmap_sg() (take 2)

Use ide_destroy_dmatable() in:
* ide-dma.c::ide_build_dmatable()
* sgiioc4.c::sgiioc4_build_dma_table()
* pmac.c::pmac_ide_{build,destroy}_dmatable()

There should be no functionality changes caused by this patch.

v2:
* pmac.c build fix from Andrew Morton.

Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>