regulator: bd9571mwv: Convert device attribute to sysfs_emit()

Convert the "backup_mode" device attribute from sprintf() to
sysfs_emit(), as the latter is aware of the PAGE_SIZE buffer.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210312130242.3390038-4-geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/bd9571mwv-regulator.c

@@ -174,7 +174,7 @@ static ssize_t backup_mode_show(struct device *dev,
 {
 	struct bd9571mwv_reg *bdreg = dev_get_drvdata(dev);
 
-	return sprintf(buf, "%s\n", bdreg->bkup_mode_enabled ? "on" : "off");
+	return sysfs_emit(buf, "%s\n", bdreg->bkup_mode_enabled ? "on" : "off");
 }
 
 static ssize_t backup_mode_store(struct device *dev,