fwk: marigold: clear rtc flag when force shutdown

When we force shutdown, the unit should be forced to G3.
so clearing RTC flags will ensure we do not get stuck at keep_pch_power.

When system hangs before into s4, RTC wake flags will be set up, when
this moment forces shutdown Unit will stuck at S4, and EC will push the
solution for force shutdown can't power on.

BRANCH=fwk-main
BUG=[86equnzvk](https://app.clickup.com/t/86equnzvk)
TEST=test on marigold, setup RTC flags by EC cmd (memmap set 0x102 1),
and do force shutdown(8s), press power button make sure unit can power up

Signed-off-by: LeoCX_Tsai <LeoCX_Tsai@compal.com>
(cherry picked from commit 841cbe9)

Author: LeoCX-Tsai

zephyr/program/framework/marigold/src/power_sequence.c

@@ -262,6 +262,7 @@ void chipset_force_shutdown(enum chipset_shutdown_reason reason)
 		report_ap_reset(reason);
 		force_g3_flags = 1;
 		chipset_force_g3();
+		clear_rtcwake();
 	}
 }