dmaengine: shdma: fix DMA error handling.

Present DMA error ISR in shdma.c is bogus, it locks the system hard in multiple
ways. Fix it to abort all queued transactions on all channels on the affected
controller and giving submitters a chance to get a DMA_ERROR status for aborted
transactions. Afterwards further functionality is again possible without the
need to re-load the driver.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>