Convert CONFIG_SPLASH_SCREEN et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPLASH_SCREEN
   CONFIG_SPLASH_SCREEN_ALIGN
   CONFIG_SPLASHIMAGE_GUARD
   CONFIG_SPLASH_SOURCE

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/odroid-c4_defconfig b/configs/odroid-c4_defconfig
index 4d112d3..bf79d74 100644
--- a/configs/odroid-c4_defconfig
+++ b/configs/odroid-c4_defconfig
@@ -58,4 +58,6 @@
 CONFIG_DM_VIDEO=y
 CONFIG_VIDEO_MESON=y
 CONFIG_VIDEO_DT_SIMPLEFB=y
+CONFIG_SPLASH_SCREEN=y
+CONFIG_SPLASH_SCREEN_ALIGN=y
 CONFIG_OF_LIBFDT_OVERLAY=y