dmaengine: xilinx: xdma: Use resource_size() in xdma_probe()

There is a warning reported by coccinelle:

./drivers/dma/xilinx/xdma.c:888:22-25: ERROR:
	Missing resource_size with   res

Use resource_size() on resource object instead of explicit computation.

Signed-off-by: Li Zetao <lizetao1@huawei.com>
Link: https://lore.kernel.org/r/20230803033235.3049137-1-lizetao1@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>