x86: Enable generic board support

This enables generic board support so that x86 boards can define
CONFIG_SYS_GENERIC_BOARD.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 9b24dc5f..ee89354 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -25,7 +25,10 @@
 
 LIB	= $(obj)lib$(ARCH).o
 
+ifeq ($(CONFIG_SYS_GENERIC_BOARD),)
 COBJS-y	+= board.o
+endif
+
 COBJS-y	+= bootm.o
 COBJS-y	+= cmd_boot.o
 COBJS-y	+= gcc.o