x86: Enable the RTC on all boards

With the move to Kconfig this option should be set in Kconfig, not in the
config header file. Move it.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

arch/Kconfig

@@ -165,6 +165,7 @@ config X86
 	imply USB_ETHER_SMSC95XX
 	imply USB_HOST_ETHER
 	imply PCH
+	imply RTC_MC146818
 
 	# Thing to enable for when SPL/TPL are enabled: SPL
 	imply SPL_DM

include/configs/x86-common.h

@@ -36,7 +36,6 @@
 /*-----------------------------------------------------------------------
  * Real Time Clock Configuration
  */
-#define CONFIG_RTC_MC146818
 #define CONFIG_SYS_ISA_IO_BASE_ADDRESS	0
 #define CONFIG_SYS_ISA_IO      CONFIG_SYS_ISA_IO_BASE_ADDRESS