treewide: Migrate CONFIG_BOARD_EARLY_INIT_R to Kconfig

Migrate the CONFIG_BOARD_EARLY_INIT_R option to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/strider_con_defconfig b/configs/strider_con_defconfig
index 17fe2fa..f024e47 100644
--- a/configs/strider_con_defconfig
+++ b/configs/strider_con_defconfig
@@ -13,6 +13,7 @@
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_BOARD_EARLY_INIT_R=y
 CONFIG_HUSH_PARSER=y
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_STOP_STR=" "