libmsc: remove 'deferred' parameter in sms_route_mt_sms()

No need to cache the sms object, just cache what we need into the
smpp_cmd structure. This simplifies what that I introduced in
93ffbd0029d1 ("libmsc: send RP-ACK to MS after ESME sends SMPP
DELIVER-SM-RESP").

Change-Id: Iba5f864f9bb963baff95969e306b1b7cff00c1e3
3 files changed