Use a separate fd set for select()-s exception fds param to fix the
following gcc warning:

  pager.c:36:12: error: passing argument 2 to restrict-qualified parameter aliases with argument 4 [-Werror=restrict]
    select(1, &in, NULL, &in, NULL);
              ^~~        ~~~

Link: http://lkml.kernel.org/r/20180101105626.7168-1-sergey.senozhatsky@gmail.comSigned-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>