x86-32: move _end to a dummy section

Impact: build fix with CONFIG_RELOCATABLE

Move _end into a dummy section, so that relocs.c will know it is a
relocatable symbol.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>

arch/x86/kernel/vmlinux_32.lds.S

@@ -199,7 +199,9 @@ SECTIONS
 	__brk_limit = . ;
   }
 
-  _end = . ;
+  .end : AT(ADDR(.end) - LOAD_OFFSET) {
+	_end = . ;
+  }
 
   /* Sections to be discarded */
   /DISCARD/ : {