driver core: platform: need consistent spacing around '-'

Fix the below checkpatch issue:

ERROR: need consistent spacing around '-' (ctx:WxV)
FILE: drivers/base/platform.c:1008:
+       len = acpi_device_modalias(dev, buf, PAGE_SIZE -1);
                                                       ^
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20200602045556.66948-1-song.bao.hua@hisilicon.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -1019,7 +1019,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
 	if (len != -ENODEV)
 		return len;
 
-	len = acpi_device_modalias(dev, buf, PAGE_SIZE -1);
+	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
 	if (len != -ENODEV)
 		return len;