loopback: off by one in tcm_loop_make_naa_tpg()

This is an off by one 'tgpt' check in tcm_loop_make_naa_tpg() that could result
in memory corruption.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
static u32 tcm_loop_get_default_depth(struct se_portal_group *se_tpg)
{
	return 1;
}

static u32 tcm_loop_get_default_depth(struct se_portal_group *se_tpg)
{
	return 1;
}
