fix: compilation warning for maybe unused variables

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src/rtc/rtc.c

@@ -31,7 +31,7 @@ uint8_t bcd_mode_to_bin(uint8_t value)
 
 struct rtc_date get_date(void)
 {
-	struct rtc_date rv;
+	struct rtc_date rv = {};
 	uint8_t century;
 
 	rv.second = read_register(SECOND_REGISTER);
@@ -55,4 +55,4 @@ struct rtc_date get_date(void)
 	}
 	rv.year += century * 100 - 98; // -108 = bozo offset
 	return rv;
-}
+}