dmaengine: dw: fix cyclic transfer callbacks

Cyclic transfer callbacks rely on block completion interrupts which were
disabled in commit ff7b05f2 ("dmaengine/dw_dmac: Don't handle block
interrupts").  This re-enables block interrupts so the cyclic callbacks
can work.  Other transfer types are not affected as they set the INT_EN
bit only on the last block.

Fixes: ff7b05f2 ("dmaengine/dw_dmac: Don't handle block interrupts")
Signed-off-by: Mans Rullgard <mans@mansr.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Cc: <stable@vger.kernel.org>