xt_qtaguid: use sock_gen_put() instead of xt_socket_put_sk()

Removing obsolete xt_socket_put_sk() and using sock_gen_put() instead.
xt_socket_put_sk() was reintroduced for xt_qtaguid in one of the patches,
but it turned out sock_gen_put() supersedes xt_socket_put_sk(). So we
don't need xt_socket_put_sk() any more.

This patch is based on commit 1a8bf6ee (netfilter: xt_socket: use sock_gen_put())

Change-Id: I976d5f7f7eded0f3cc91b596acfeb35e4c2057e5
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
(cherry picked from commit 551780fc28cb7480dbc4f585ef80ca02c2922ec1)
Signed-off-by: John Stultz <john.stultz@linaro.org>