USSD: don't use gsm0480_msgb_alloc_name()

We have nothing to do with GSM 04.80 at the HLR - it's only used to
encapsulate the SS payload between MS and MSC. This is not that
critical, but may be misleading.

Also, gsm0480_msgb_alloc_name() allocates a smaller buffer:

  return msgb_alloc_headroom(1024, 128, name);

than osmo_gsup_client_msgb_alloc() does:

  return msgb_alloc_headroom(4000, 64, __func__);

Change-Id: Icdab40c6a933888eb9f51bee9c5264c8919dbf7b
1 file changed