x86: Use sections header to obtain link symbols

These are defined in asm-generic/sections.h, so remove them from
architecture-specific files.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/board.c b/arch/x86/lib/board.c
index 555301a..452e5d8 100644
--- a/arch/x86/lib/board.c
+++ b/arch/x86/lib/board.c
@@ -38,6 +38,7 @@
 #include <asm/u-boot-x86.h>
 #include <asm/relocate.h>
 #include <asm/processor.h>
+#include <asm/sections.h>
 
 #include <asm/init_helpers.h>
 #include <asm/init_wrappers.h>