OMAP: DSS2: OMAPFB: Fix sysfs mirror input check

Using bool silently converted input to 0 or 1, making the range check
useless. Use unsigned long instead, and convert to bool later. Found by
Coverity.
Signed-off-by: NJani Nikula <ext-jani.1.nikula@nokia.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

drivers/video/omap2/omapfb/omapfb-sysfs.c

@@ -102,7 +102,7 @@ static ssize_t store_mirror(struct device *dev,
 {
 	struct fb_info *fbi = dev_get_drvdata(dev);
 	struct omapfb_info *ofbi = FB2OFB(fbi);
-	bool mirror;
+	unsigned long mirror;
 	int r;
 	struct fb_var_screeninfo new_var;