x86, vdso: Finish removing VDSO32_PRELINK

It's a declaration of a nonexistent symbol.  We can get rid of the
64-bit versions, too, but that's more intrusive.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Stefani Seibold <stefani@seibold.net>
Link: http://lkml.kernel.org/r/2ce2ce18447d8a0b78d44a278a066b6c0af06b32.1395366931.git.luto@amacapital.netSigned-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/vdso.h

@@ -41,8 +41,6 @@ DECLARE_VDSO_IMAGE(vdso32_syscall);
 #endif
 DECLARE_VDSO_IMAGE(vdso32_sysenter);
 
-extern const char VDSO32_PRELINK[];
-
 /*
  * Given a pointer to the vDSO image, find the pointer to VDSO32_name
  * as that symbol is defined in the vDSO sources or linker script.