drivers/video/backlight/lp855x_bl.c: use PAGE_SIZE for the sysfs read operation

sysfs allocates PAGE_SIZE.  It is used by each R/W operation method.  Use
it instead of another buffer size.
Signed-off-by: NMilo(Woogyom) Kim <milo.kim@ti.com>
Acked-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/backlight/lp855x_bl.c

@@ -35,7 +35,6 @@
 #define LP8557_EPROM_START		0x10
 #define LP8557_EPROM_END		0x1E
 
-#define BUF_SIZE		20
 #define DEFAULT_BL_NAME		"lcd-backlight"
 #define MAX_BRIGHTNESS		255
 
@@ -304,7 +303,7 @@ static ssize_t lp855x_get_chip_id(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
 	struct lp855x *lp = dev_get_drvdata(dev);
-	return scnprintf(buf, BUF_SIZE, "%s\n", lp->chipname);
+	return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
 }
 
 static ssize_t lp855x_get_bl_ctl_mode(struct device *dev,
@@ -319,7 +318,7 @@ static ssize_t lp855x_get_bl_ctl_mode(struct device *dev,
 	else if (mode == REGISTER_BASED)
 		strmode = "register based";
 
-	return scnprintf(buf, BUF_SIZE, "%s\n", strmode);
+	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
 }
 
 static DEVICE_ATTR(chip_id, S_IRUGO, lp855x_get_chip_id, NULL);