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/colibri_vf_defconfig b/configs/colibri_vf_defconfig
index a67e2e2..b145b9f 100644
--- a/configs/colibri_vf_defconfig
+++ b/configs/colibri_vf_defconfig
@@ -96,6 +96,7 @@
 # CONFIG_VIDEO_BPP8 is not set
 # CONFIG_VIDEO_BPP16 is not set
 CONFIG_VIDEO_FSL_DCU_FB=y
+CONFIG_SPLASH_SCREEN_ALIGN=y
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_FDT_FIXUP_PARTITIONS=y
 # CONFIG_EFI_UNICODE_CAPITALIZATION is not set