UBUNTU: SAUCE: fix yama_ptracer_del lockdep warning

UBUNTU: SAUCE: fix yama_ptracer_del lockdep warning

yama_ptracer_del can be called in softirq context, so
ptracer_relations_lock may be held in softirq context.

This patch replaces spin_[un]lock with spin_[un]lock_bh for
&ptracer_relations_lock to fix reported lockdep warning and
avoid possible dealock.

BugLink: http://bugs.launchpad.net/bugs/791019

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>