[PATCH] tty: Fix two reported pid leaks

These leaks were reported by: Catalin Marinas <catalin.marians@gmail.com>
and I have been able to very by inspection they are possible.

When converting tty_io.c to store pids as struct pid pointers instead
of pid_t values it appears I overlooked two places where we stop using
the pid value.  The very obvious one is in do_tty_hangup, and the one
the less obvious one in __proc_set_tty.

When looking into the code __proc_set_tty only has pids that need to
be put because of failures of other parts of the code to properly
perform hangup processing.   Fixing the leak here in __proc_set_tty
is easy and obviously correct so I am doing that first.

Fixing the places that should be performing hangup processing is much
less obviously correct.  So those I'm aiming those patches at -mm.
for now, so the can age a while before they are merged.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>