boards/sim/sim/sim/nsh: enable CONFIG_RTC so date command shows host time

The default sim:nsh config has no RTC, causing NSH_DISABLE_DATE to be
auto-enabled (default: DEFAULT_SMALL || !RTC). This means the date
command is not compiled in, and the system time defaults to a hardcoded
value instead of syncing with the host.

Enable CONFIG_RTC, CONFIG_RTC_DRIVER, and CONFIG_RTC_ARCH in the
sim:nsh defconfig so the date command is available and shows the
correct host time out of the box.

Author: hanzj

boards/sim/sim/sim/configs/nsh/defconfig

@@ -72,3 +72,7 @@ CONFIG_SYSTEM_DUMPSTACK=y
 CONFIG_SYSTEM_GCOV=y
 CONFIG_SYSTEM_NSH=y
 CONFIG_TESTING_OSTEST=y
+
+CONFIG_RTC=y
+CONFIG_RTC_DRIVER=y
+CONFIG_RTC_ARCH=y