dmaengine: Fix choppy sound because of unimplemented resume

Some drivers implement only pause operation (no resuming). Example is
pl330 where pause is needed for getting residuum. pl330 does not support
resume operation, transfer must be stopped after pause.

However for slaves this is exposed always as "pause and resume" which
introduces subtle errors on Odroid U3 board (Exynos4412 with pl330).
After adding pause function to pl330 driver the audio playback
(utilizing DMA) gets choppy after some time (approximately 24 hours).

Fix this by exposing "cmd_pause" if and only if pause and resume are
implemented.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reported-by:  <gabriel@unseen.is>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: <stable@vger.kernel.org>
Fixes: 88987d2c ("dmaengine: pl330: add DMA_PAUSE feature")
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>