staging: lirc_sasem: fix NULL pointer dereference in sasem_probe

If any memory allocation failed, goto alloc_status_switch
leads to mutex_unlock(&context->ctx_lock) while context is NULL.
The patch moves alloc_status_switch to handle error conditions
in correct way.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>