loopback: Fix memory leak in tcm_loop_make_scsi_hba()

There is a memory leak in tcm_loop_make_scsi_hba().

If all the strstr() calls return NULL and we end up at return ERR_PTR(-EINVAL);
then we'll be leaking the memory previously allocated to tl_hba as
that variable goes out of scope.

This patch should fix the leak.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>