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/eb_cpu5282_defconfig b/configs/eb_cpu5282_defconfig
index 65bc7a0..339366b 100644
--- a/configs/eb_cpu5282_defconfig
+++ b/configs/eb_cpu5282_defconfig
@@ -34,3 +34,4 @@
 CONFIG_MII=y
 CONFIG_VIDEO=y
 # CONFIG_CFB_CONSOLE is not set
+CONFIG_SPLASH_SCREEN=y