ms: Merge ms_storage into bts.cpp

That class is mostly a C++ class holding a llist plus some callbacks.
Having that in a separate class makes code more complex for no good
reason. This patch moves the llist into bts and allocates stuff directly
from within bts.
This will allow further cleanup of MS lieficyle in future patches.

Change-Id: I627f5db5073189c23ddf2b7f09c90abb24846f62
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 8980d8e..cca059a 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -27,7 +27,6 @@
 #include <decoding.h>
 #include <encoding.h>
 #include <gprs_ms.h>
-#include <gprs_ms_storage.h>
 #include <llc.h>
 #include "pcu_utils.h"
 
@@ -199,12 +198,12 @@
 	GprsMs *ms, *ms_old;
 
 	/* check for existing TBF */
-	ms = bts_ms_store(bts)->get_ms(tlli, tlli_old, imsi);
+	ms = bts_get_ms(bts, tlli, tlli_old, imsi);
 
 	/* If we got MS by TLLI above let's see if we already have another MS
 	 * object identified by IMSI and merge them */
 	if (ms && !ms_imsi_is_valid(ms) && imsi) {
-		ms_old = bts_ms_store(bts)->get_ms(GSM_RESERVED_TMSI, GSM_RESERVED_TMSI, imsi);
+		ms_old = bts_get_ms_by_imsi(bts, imsi);
 		if (ms_old && ms_old != ms) {
 			/* The TLLI has changed (RAU), so there are two MS
 			 * objects for the same MS */