ea20: Convert to generic board

Boards need to select CONFIG_SYS_GENERIC_BOARD in order to
prevent removal from the project.
Signed-off-by: NStefano Babic <sbabic@denx.de>

include/configs/ea20.h

@@ -24,6 +24,8 @@
 #define CONFIG_VIDEO
 #define CONFIG_PREBOOT
 
+#define CONFIG_SYS_GENERIC_BOARD
+
 /*
  * SoC Configuration
  */