mmc: dw_mmc: fix the wrong condition check of getting num-slots from DT

Change to print the information about when the deprecated "num-slots" DT
binding is being used, as to avoid confusion when browsing the log:

dwmmc_rockchip fe320000.dwmmc: 'num-slots' was deprecated.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Fixes: d30a8f7b ("mmc: dw_mmc: deprecated the "num-slots" property")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/dw_mmc.c

@@ -2957,7 +2957,7 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
 	}
 
 	/* find out number of slots supported */
-	if (device_property_read_u32(dev, "num-slots", &pdata->num_slots))
+	if (!device_property_read_u32(dev, "num-slots", &pdata->num_slots))
 		dev_info(dev, "'num-slots' was deprecated.\n");
 
 	if (device_property_read_u32(dev, "fifo-depth", &pdata->fifo_depth))