rename bscconfig.h to config.h, cleanup

Get rid of the legacy name bscconfig.h from osmo-nitb times.

Remove the #include from some of the files that aren't actually using it.

Instead of '#include "../../config.h"', use plain '#include "config.h"'
because we're anyway passing $top_srcdir as -I during compilation.

Change-Id: Id4f683be1f36f0630c83da54e02868aae847aeec
diff --git a/src/libmsc/gsm_04_11.c b/src/libmsc/gsm_04_11.c
index 60cdaee..ff5576f 100644
--- a/src/libmsc/gsm_04_11.c
+++ b/src/libmsc/gsm_04_11.c
@@ -33,7 +33,7 @@
 #include <time.h>
 #include <netinet/in.h>
 
-#include "bscconfig.h"
+#include "config.h"
 
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/talloc.h>