dma: xilinx_dpdma: Remove unnecessary use of irqsave/restore

xilinx_dpdma_chan_done_irq and xilinx_dpdma_chan_vsync_irq are always
called with IRQs disabled from xilinx_dpdma_irq_handler. Therefore we
don't need to save/restore the IRQ flags.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://lore.kernel.org/r/20240308210034.3634938-3-sean.anderson@linux.dev
Signed-off-by: Vinod Koul <vkoul@kernel.org>