drm/panel: Convert sysfs sprintf/snprintf family to sysfs_emit

Fix the following coccicheck warning:
drivers/gpu/drm/panel//panel-tpo-td043mtea1.c:217:8-16: WARNING:
use scnprintf or sprintf
drivers/gpu/drm/panel//panel-tpo-td043mtea1.c:189:8-16: WARNING:
use scnprintf or sprintf
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1617069288-8317-1-git-send-email-tiantao6@hisilicon.com

drivers/gpu/drm/panel/panel-tpo-td043mtea1.c

@@ -186,7 +186,7 @@ static ssize_t vmirror_show(struct device *dev, struct device_attribute *attr,
 {
 	struct td043mtea1_panel *lcd = dev_get_drvdata(dev);
 
-	return snprintf(buf, PAGE_SIZE, "%d\n", lcd->vmirror);
+	return sysfs_emit(buf, "%d\n", lcd->vmirror);
 }
 
 static ssize_t vmirror_store(struct device *dev, struct device_attribute *attr,
@@ -214,7 +214,7 @@ static ssize_t mode_show(struct device *dev, struct device_attribute *attr,
 {
 	struct td043mtea1_panel *lcd = dev_get_drvdata(dev);
 
-	return snprintf(buf, PAGE_SIZE, "%d\n", lcd->mode);
+	return sysfs_emit(buf, "%d\n", lcd->mode);
 }
 
 static ssize_t mode_store(struct device *dev, struct device_attribute *attr,