do_pipe cleanup: drop its last user in arch/alpha/

The last user of do_pipe is in arch/alpha/, after replacing it with
do_pipe_flags, the do_pipe can be totally dropped.

Signed-off-by: Cheng Renquan <crquan@gmail.com>
Acked-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/pipe.c

@@ -1034,11 +1034,6 @@ int do_pipe_flags(int *fd, int flags)
 	return error;
 }
 
-int do_pipe(int *fd)
-{
-	return do_pipe_flags(fd, 0);
-}
-
 /*
  * sys_pipe() is the normal C calling standard for creating
  * a pipe. It's not the way Unix traditionally does this, though.