spi: dw: fixed missing resource_size

fixed the coccicheck:
drivers/spi/spi-dw-bt1.c:220:27-30: ERROR: Missing
resource_size with mem.
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Acked-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/1606114975-31362-1-git-send-email-tiantao6@hisilicon.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-bt1.c

@@ -217,7 +217,7 @@ static int dw_spi_bt1_sys_init(struct platform_device *pdev,
 	if (mem) {
 		dwsbt1->map = devm_ioremap_resource(&pdev->dev, mem);
 		if (!IS_ERR(dwsbt1->map)) {
-			dwsbt1->map_len = (mem->end - mem->start + 1);
+			dwsbt1->map_len = resource_size(mem);
 			dws->mem_ops.dirmap_create = dw_spi_bt1_dirmap_create;
 			dws->mem_ops.dirmap_read = dw_spi_bt1_dirmap_read;
 		} else {