rtc: mt2712: fix build without PM_SLEEP

Fix this build error when PM_SLEEP is not selected:

drivers/rtc/rtc-mt2712.c:412:10: error: ‘mt2712_pm_ops’ undeclared here (not in a function); did you mean ‘mt2712_rtc_ops’?
  412 |   .pm = &mt2712_pm_ops,
      |          ^~~~~~~~~~~~~

Link: https://lore.kernel.org/r/20200317143421.9551-1-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-mt2712.c

@@ -409,7 +409,9 @@ static struct platform_driver mt2712_rtc_driver = {
 	.driver = {
 		.name = "mt2712-rtc",
 		.of_match_table = mt2712_rtc_of_match,
+#ifdef CONFIG_PM_SLEEP
 		.pm = &mt2712_pm_ops,
+#endif
 	},
 	.probe  = mt2712_rtc_probe,
 };