x86: vdso/vma.c declare vdso_enabled and arch_setup_additional_pages before they get used

Impact: cleanup, address sparse warnings

Addresses the problem pointed out by these sparse warning:
  arch/x86/vdso/vma.c:19:28: warning: symbol 'vdso_enabled' was not declared. Should it be static?
  arch/x86/vdso/vma.c:101:5: warning: symbol 'arch_setup_additional_pages' was not declared. Should it be static?
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
LKML-Reference: <1239548845.4170.2.camel@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/vdso/vma.c

@@ -8,6 +8,7 @@
 #include <linux/sched.h>
 #include <linux/init.h>
 #include <linux/random.h>
+#include <linux/elf.h>
 #include <asm/vsyscall.h>
 #include <asm/vgtod.h>
 #include <asm/proto.h>