dmaengine: add verification of DMA_INTERRUPT capability for dmatest

dmaengine: add verification of DMA_INTERRUPT capability for dmatest

Looks like I forgot to add DMA_INTERRUPT cap setting to the idxd driver and
dmatest is still working regardless of this mistake. Add an explicit check
of DMA_INTERRUPT capability for dmatest to make sure the DMA device being used
actually supports interrupt before the test is launched and also that the
driver is programmed correctly.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/164978679251.2361020.5856734256126725993.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>