alpha: Fix duplicate <asm/thread_info.h> include

.. duplicated by merging the same fix twice, for details see commit
0d9df251 ("Merge
git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild-fixes")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/kernel/vmlinux.lds.S

 #include <asm-generic/vmlinux.lds.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
-#include <asm/thread_info.h>
 
 OUTPUT_FORMAT("elf64-alpha")
 OUTPUT_ARCH(alpha)