Convert CONFIG_ARCH_EARLY_INIT_R to Kconfig

This converts the following to Kconfig:
   CONFIG_ARCH_EARLY_INIT_R

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index bb1a818..0b64e1d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -12,6 +12,7 @@
 	bool "ARC architecture"
 	select HAVE_PRIVATE_LIBGCC
 	select SUPPORT_OF_CONTROL
+	select ARCH_EARLY_INIT_R
 
 config ARM
 	bool "ARM architecture"