x86: Move do_go_exec() out of board.c

--
Changes for v2:
 - None
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index d584aa4..7820895 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -32,6 +32,7 @@
 COBJS-$(CONFIG_SYS_PC_BIOS)	+= bios_setup.o
 COBJS-y	+= board.o
 COBJS-y	+= bootm.o
+COBJS-y	+= cmd_boot.o
 COBJS-y	+= gcc.o
 COBJS-y	+= interrupts.o
 COBJS-$(CONFIG_SYS_PCAT_INTERRUPTS) += pcat_interrupts.o