x86: Enable RTC command by default

The real-time clock is needed for most X86 systems and it is useful to
be able to read from it. Enable the rtc command by default.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index bff22b94..a4ca61c 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2291,6 +2291,7 @@
 config CMD_RTC
 	bool "rtc"
 	depends on DM_RTC
+	default y if X86
 	help
 	  Enable the 'rtc' command for low-level access to RTC devices.