llme_free: clean up related sndcp

Fix crash in vty_dump_sne when sndcp->lle has already been deallocated.

Context:
* sndcp->lle is set only once in gprs_sndcp_entity_alloc()
* sndcp->lle is a struct gprs_llc_lle, which gets allocated and
  deallocated together with struct gprs_llc_llme. From gprs_llc.h:

    struct gprs_llc_llme {
            ...
            struct gprs_llc_lle lle[NUM_SAPIS];

Fixes: OS#4824
Change-Id: I707029f78222bc6335837241e5a08c54c5ae6eb3
3 files changed