rtc: brcmstb-waketimer: quiet maybe-unused variable warning

When CONFIG_OF is disabled then the matching table is not referenced.

Signed-off-by: Alexandre Belloni <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/rtc/rtc-brcmstb-waketimer.c

···
 static SIMPLE_DEV_PM_OPS(brcmstb_waketmr_pm_ops,
 			 brcmstb_waketmr_suspend, brcmstb_waketmr_resume);
 
-static const struct of_device_id brcmstb_waketmr_of_match[] = {
+static const __maybe_unused struct of_device_id brcmstb_waketmr_of_match[] = {
 	{ .compatible = "brcm,brcmstb-waketimer" },
 	{ /* sentinel */ },
 };