Simplify TS alloc: move slot assignment

Move into separate functions:
* move timeslot reservation
* move UL timeslot assignment
* move DL timeslot assignment

Change-Id: I64cf78c5cfc78664766f9769dd5cde632dab92b0
Related: OS#2282
diff --git a/src/mslot_class.h b/src/mslot_class.h
index 97b865b..445455f 100644
--- a/src/mslot_class.h
+++ b/src/mslot_class.h
@@ -56,3 +56,4 @@
 int8_t find_free_usf(uint8_t usf_map);
 int8_t find_free_tfi(uint32_t tfi_map);
 void masked_override_with(char *buf, uint8_t mask, char set_char);
+void ts_format(char *buf, uint8_t dl_mask, uint8_t ul_mask);