x86: Fix incorrect usage of relocation offset

x86 has always used relocation offset in the opposite sense to the ELF
standard - Fix this
diff --git a/arch/i386/cpu/start.S b/arch/i386/cpu/start.S
index fd018bf..0031389 100644
--- a/arch/i386/cpu/start.S
+++ b/arch/i386/cpu/start.S
@@ -120,7 +120,7 @@
 
 	/* Setup call address of in-RAM copy of board_init_r() */
 	movl	$board_init_r, %ebp
-	subl	(GD_RELOC_OFF * 4)(%edx), %ebp
+	addl	(GD_RELOC_OFF * 4)(%edx), %ebp
 
 	/* Setup parameters to board_init_r() */
 	movl	%edx, %eax