dmaengine: zynqmp_dma: replace spin_lock_bh with spin_lock_irqsave

All device_prep_dma_* functions and device_issue_pending can be called
from an interrupt context. As this includes hard IRQs, we must use
spin_lock_irqsave() instead of spin_lock_bh() to access chan->lock.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Vinod Koul <vkoul@kernel.org>