dmaengine: idma64: replace spin_lock_irqsave with spin_lock

idma64_chan_irq() is invoked in hardirq handle function, it is unnecessary
to call spin_lock_irqsave.

Signed-off-by: Zhaoxiong Yuan <yuanzhx326@gmail.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>