asmlinkage: Make main_extable_sort_needed visible

main_extable_sort_needed is used by the build system and needs
to be a normal ELF symbol. Make it visible so that LTO
does not remove or mangle it.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391845930-28580-8-git-send-email-ak@linux.intel.comSigned-off-by: H. Peter Anvin <hpa@linux.intel.com>

kernel/extable.c

@@ -36,7 +36,7 @@ extern struct exception_table_entry __start___ex_table[];
 extern struct exception_table_entry __stop___ex_table[];
 
 /* Cleared by build time tools if the table is already sorted. */
-u32 __initdata main_extable_sort_needed = 1;
+u32 __initdata __visible main_extable_sort_needed = 1;
 
 /* Sort the kernel's built-in exception table */
 void __init sort_main_extable(void)