libmsc/gsm_04_11.c: do not abuse LOG_TRANS() in gsm411_alloc_mt_trans()

This change is similar to I6b68a0f0b32eb126e0f7e914a314130254d28467.
If we 100% sure that trans == NULL, it makes more sense to use
generic LOGP(DLSMS, LOGL_*, ...) call, so the logs can reflect
more information than such dummy prefix:

  trans(NULL NULL callref-0x0 tid-0) ...

Change-Id: I3c1e633aee5dd7cd0d367404a3def9cffe0b3baa
1 file changed