dmaengine: idma64: drop IRQ enable / disable in handler

There is no need to disable interrupts in the IRQ handler. The driver
guarantess that at one time only one descriptor is active, besides the fact
that each call to the same channel will be serialized in idma64_chan_irq()
handler anyway.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>