dmaengine: milbeaut-xdmac: remove redundant irqsave and irqrestore in hardIRQ

Running in hardIRQ, disabling IRQ is redundant since hardIRQ has disabled
IRQ. This patch removes the irqsave and irqstore to save some instruction
cycles.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20201027215252.25820-6-song.bao.hua@hisilicon.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>