dmaengine: sf-pdma: apply proper spinlock flags in sf_pdma_prep_dma_memcpy()

The second parameter of spinlock_irq[save/restore] function is flags,
which is the last input parameter of sf_pdma_prep_dma_memcpy().

So declare local variable 'iflags' to be used as the second parameter of
spinlock_irq[save/restore] function.

Signed-off-by: Austin Kim <austin.kim@lge.com>
Link: https://lore.kernel.org/r/20210611065336.GA1121@raspberrypi


Signed-off-by: Vinod Koul <vkoul@kernel.org>