x86, vdso: Unmap vdso pages

We mapped vdso pages but never unmapped them and the virtual address
is lost after exiting from the function, so unmap vdso pages here.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
LKML-Reference: <20100802004934.GA2505@sli10-desk.sh.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/vdso/vma.c

@@ -67,6 +67,7 @@ static int __init init_vdso_vars(void)
 	*(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x;
 #include "vextern.h"
 #undef VEXTERN
+	vunmap(vbase);
 	return 0;
 
  oom: