l1gprs/l1ctl: Decouple RTS.ind from DL_BLOCK.ind

Before this patch, the RTS:ind was crafted up in the stack when
receiving the DL_BLOCK.ind. This created some problems since the
internal low level state has to be updated in between signalling
DL_BLOCK.ind and RTS.ind, as there's a fn-advnace of one block between
those 2 signals (hence the timeslot allocation has to be applied at the
time when the fn-advance is applied).
This is actually not fixing the whole issue, since there's several
timeslots and hence the following events will have the internal timeslot updated
during the event in the middle, hence potentially causing problems in the
remaining TS:
DL_BLOCK.ind(FN=N, TS=1),  RTS.ind(FN=N+4, TS=1), DL_BLOCK.ind(FN=N, TS=2)

In any case, this decoupling already improves the situation and is step
needed anyway towards fully fixing the problem (by, for instance,
maintaining a timeslot state duplicated both for DL and Ul directions,
since they drive based on differnet FN time (1 PDCH block).

Change-Id: I1494e0aac7555f6e01b4b435b77140afc42c098e
---
M include/l1ctl_proto.h
M include/l1gprs.h
M src/host/layer23/include/osmocom/bb/common/ms.h
M src/host/layer23/include/osmocom/bb/modem/grr.h
M src/host/layer23/src/common/l1ctl.c
M src/host/layer23/src/modem/grr.c
M src/host/layer23/src/modem/rlcmac.c
M src/host/trxcon/src/trxcon_fsm.c
M src/host/virt_phy/src/virt_prim_pdch.c
M src/shared/l1gprs.c
10 files changed, 153 insertions(+), 12 deletions(-)