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: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index 2914567..0ad3867 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -165,6 +165,7 @@
 	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
diff --git a/include/configs/x86-common.h b/include/configs/x86-common.h
index 4180b25..7fcf76a 100644
--- a/include/configs/x86-common.h
+++ b/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