siimage: use ide_dma_test_irq() (take 2)

Remove interrupt bit test (not trusted anyway) from siimage_io_dma_test_irq()
and siimage_mmio_dma_test_irq() -- this allows to replace the former function
with now identical ide_dma_test_irq()...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>