x86: Enable generic board

This will be used exclusively on x86, so enable it for the whole
architecture.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/include/asm/config.h

@@ -21,4 +21,5 @@
 #ifndef _ASM_CONFIG_H_
 #define _ASM_CONFIG_H_
 
+#define CONFIG_SYS_GENERIC_BOARD
 #endif